Abstract:
Various enhancements are made to the architecture of a list processor to facilitate its use in implementing a message queue that is shared by queue managers residing across a multisystem complex. A new list structure control—a program list entry identifier indicator, or PLEIDI—is defined to allow the user to specify whether user-defined entry IDs are used when the list is allocated. A new delete list (DL) command is added that sequentially processes list entries in the order in which they exist on the specified list. A new move list entries (MLES) command provides a performance-optimized means to process an input list of entries. New key comparison functions and list monitoring enhancements have also been added. A new type of key called a secondary list entry key (SLEK) allows the user to specify a secondary key value as a means to identify a list entry.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is related to the following commonly owned copending applications, incorporated herein by reference:
         D. A. Elko et al., Ser. No. 09/677,341 filed concurrently herewith, entitled “METHOD AND APPARATUS FOR IMPLEMENTING A SHARED MESSAGE QUEUE USING A LIST STRUCTURE”;   P. Kettley et al., Ser. No. 09/605,589, filed Jun. 28, 2000, entitled “METHOD AND APPARATUS FOR OPERATING A COMPUTER SYSTEM TO ENABLE A RESTART”;   P. Kettley et al., Ser. No. 60/220,685, filed Jul. 25, 2000, entitled “METHOD AND APPARATUS FOR IMPROVING MESSAGE AVAILABILITY IN A SUBSYSTEM WHICH SUPPORTS SHARED MESSAGE QUEUES”;   D. J. Dahlen et al., Ser. No. 60/219,889, filed Jul. 21, 2000, entitled “IMPLEMENTING MQI INDEXED QUEUE SUPPORT USING COUPLING FACILITY LIST STRUCTURES”.       

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a method and apparatus for managing a list structure and, more particularly, to extensions to the architecture of a list processor that render it especially suitable for processing shared message queues. 
   2. Description of the Related Art 
   IBM&#39;s MQSeries® is a set of middleware products that allow user applications to intercommunicate using messages, without having to know the complexities of the underlying hardware and software platform. Applications communicate using the MQSeries application programming interface (API), issuing such calls as MQPUT to put a message onto a queue and MQGET to get a message from a queue. MQSeries is described in such publications as  MQSeries Planning Guide , IBM GC33-1349-07 (January 1999), incorporated herein by reference. 
   The IBM S/390® Parallel Sysplex® configuration is a cluster of interconnected processing nodes with attachments to shared storage devices, network controllers, and core cluster technology components, consisting of coupling facilities, coupling support facilities, and external time references (ETRs). A coupling facility (CF) enables high-performance read/write sharing of data by applications running on each node of the cluster through global locking and cache coherency management mechanisms. It also provides cluster-wide queuing mechanisms for workload distribution and message passing between nodes. 
   The coupling facility is described in the following patents and publications, incorporated herein by reference:
         “In a Multiprocessing System Having a Coupling Facility, Communicating Messages Between the Processors and the Coupling Facility in Either a Synchronous Operation or an Asynchronous Operation”, by D. A. Elko et al., Ser. No. 08/420,893, Filed Apr. 11, 1995, now U.S. Pat. No. 5,561,809;   “Sysplex Shared Data Coherency Method And Means”, by D. A. Elko et al., Ser. No. 07/860,805, Filed Mar. 30, 1992, now U.S. Pat. No. 5,537,574;   “Method And Apparatus For Distributed Locking Of Shared Data, Employing A Central Coupling Facility”, by D. A. Elko et al., Ser. No. 07/860,808, Filed Mar. 30, 1992, now U.S. Pat. No. 5,339,427;   “Command Quiesce Function”, by D. A. Elko et al., Ser. No. 07/860,330, Filed Mar. 30, 1992, now U.S. Pat. No. 5,339,405;   “Software Cache Management Of A Shared Electronic Store In A Sysplex”, by D. A. Elko et al., Ser. No. 07/860,807, Filed Mar. 30, 1992, now U.S. Pat. No. 5,457,793;   “Multiple Processor System Having Software For Selecting Shared Cache Entries Of An Associated Castout Class For Transfer To A DASD With One I/O Operation”, by D. A. Elko et al, Ser. No. 07/860,806, Filed Mar. 30, 1992, now U.S. Pat. No. 5,493,668;   “Command Execution System For Using First And Second Commands To Reserve And Store Second Command Related Status Information In Memory Portion Respectively”, by D. A. Elko et al., Ser. No. 07/860,378, Filed Mar. 30, 1992, now U.S. Pat. No. 5,392,397;   “Integrity Of Data Objects Used To Maintain State Information For Shared Data At A Local Complex”, by D. A. Elko et al, Ser. No. 07/860,800, Filed Mar. 30, 1992, now U.S. Pat. No. 5,331,673;   “Management Of Data Objects Used To Maintain State Information For Shared Data At A Local Complex”, by J. A. Frey et al, Ser. No. 07/860,797, Filed Mar. 30, 1992, now U.S. Pat. No. 5,388,266;   “Clearing Data Objects Used To Maintain State Information For Shared Data At A Local Complex When At Least One Message Path To The Local Complex Cannot Be Recovered”, by J. A. Frey et al., Ser. No. 07/860,647, Filed Mar. 30, 1992, now U.S. Pat. No. 5,394,542;   “Coupling Facility For Receiving Commands From Plurality Of Hosts For Activating Selected Connection Paths To I/O Devices And Maintaining Status Thereof”, by D. A. Elko. et al., Ser. No. 08/324,447, Filed Oct. 18, 1994, now U.S. Pat. No. 5,463,736;   “Data Processing System And Method For Providing Notification In A Central Processor Of State Changes For Shared Data Structure On External Storage”, by J. A. Frey et al., Ser. No. 07/860,809, Filed Mar. 30, 1992, now U.S. Pat. No. 5,390,328;   “Method And Apparatus For Performing Conditional Operations On Externally Shared Data”, by J. A. Frey et al., Ser. No. 08/383,532, Filed Feb. 1, 1995, now U.S. Pat. No. 5,742,830;   “Apparatus And Method For List Management In A Coupled Data Processing System”, by J. A. Frey et al., Ser. No. 07/860,633, Filed Mar. 30, 1992, now U.S. Pat. No. 5,410,695;   “Interdicting I/O And Messaging Operations In A Multi-System Complex”, by D. A. Elko et al., Ser. No. 07/860,489, Filed Mar. 30, 1992, now U.S. Pat. No. 5,394,554;   “Method And Apparatus For Coupling Data Processing Systems”, by D. A. Elko et al., Ser. No. 07/860,803, Filed Mar. 30, 1992, now U.S. Pat. No. 5,317,739;   “Authorization Method For Conditional Command Execution”, by D. A. Elko et al., Ser. No. 08/408,446, Filed Mar. 22, 1995, now U.S. Pat. No. 5,450,590;   “Dynamically As signing a Dump Space in a Shared Data Facility to Receive Dumping Information to be Captured”, by D. A. Elko et al., Ser. No. 08/471,895, Filed Jun. 7, 1995, now U.S. Pat. No. 5,664,155;   “Method And System For Capturing and Controlling Access To Information In A Coupling Facility”, by D. E. Neuhard et al., Ser. No. 08/146,647, filed Nov. 1, 1993, now U.S. Pat. No. 5,630,050;   “Method and System for Determining and Overriding Information Unavailability Time at a Coupling Facility”, by D. A. Neuhard et al., Serial. No. 08/779,196, filed Jan. 6, 1997, now U.S. Pat. No. 5,875,484;   “Requesting a Dump of Information Stored within a Coupling Facility, in Which the Dump Includes Serviceability Information from an Operating System That Lost Communication with the Coupling Facility”, by D. A. Neuhard et al., Serial. No. 08/779,195, filed Jan. 6, 1997, now U.S. Pat. No. 5,860,115;   “Method and Apparatus for Expansion, Contraction, and Reapportionment of Structured External Storage Structures”, by D. J. Dahlen et al., Ser. No. 08/304,458, filed Sep. 12, 1994, now U.S. Pat. No. 5,581,737;   “Method of Managing Resources in One or More Coupling Facilities Coupled to One or More Operating Systems in One or More Central Programming Complexes Using a Policy”, by R. A. Allen et al., Ser. No. 08/607,053, filed Feb. 26, 1996, now U.S. Pat. No. 5,634,072;   “Method and System for Managing Data and Users of Data in a Data Processing System”, by R. A. Allen, Ser. No. 08/146,727, filed Nov. 1, 1993, now U.S. Pat. No. 5,465,359;   “Method and System for Reconfiguring a Storage Structure Within a Structure Processing Facility”, by R. A. Allen et al., Ser. No. 08/544,941, filed Oct. 18, 1995, now U.S. Pat. No. 5,515,499;   “Method for Coordinating Executing Programs in a Data Processing System”, by R. A. Allen et al., Ser. No. 08/439,269, filed May 9, 1995, now U.S. Pat. No. 5,604,863;   “Coherence Controls for Store-Multiple Shared Data Coordinated by Cache Directory Entries in a Shared Electronic Storage”, by K. S. Carpenter et al., Ser. No. 08/148,707, filed Nov. 8, 1993, now U.S. Pat. No. 5,544,345;   “Method and System for Log Management in a Coupled Data Processing System”, by R. V. Geiner et al., Ser. No. 08/632,683, filed Apr. 15, 1996, now U.S. Pat. No. 5,737,600; and   J. M. Nick et al., “S/390 cluster technology: Parallel Sysplex”,  IBM Systems Journal , vol. 36, no. 2, 1997, pages 172-201.       

   It would be desirable to be able to use the list-processing capabilities of the coupling facility to implement a message queue that is shared by queue managers residing on different systems across a sysplex. To be suitable for this purpose, the CF list architecture should allow MQSeries to efficiently implement the following message-queuing semantics:
     1. A message must be uniquely identified.   2. A message put cannot be visible to other units of work (UOWs) until it is committed.
       When a message is written by a UOW, it must not be visible to other units of work anywhere in the queue-sharing group (QSG) until the message is committed. The uncommitted message however is available to the unit of work that wrote it.   
       3. Committed messages must be maintained in proper sequence.
       Committed messages eligible to be read must be in priority sequence, from highest priority to lowest priority. If there are multiple messages with the same priority, then the set of messages must be maintained in order of arrival sequence within designated priority.   
       4. Messages read must be unavailable to others UOWs in the QSG.
       When a committed message is read by a unit of work, then no other unit of work anywhere in the queue-sharing group can read the same message. If the message that is read is committed, it must be deleted from the CF list structure so that it is never visible again to another unit of work.   
       5. Messages read that are backed out must be reinserted into their proper committed positions with respect to both priority and time of arrival.
       If the message that was read is backed out, it must again become visible to other units of work executing in the queue-sharing group. When the message is backed out, it must be reinserted into the committed portion of a list with respect to both its priority and its time of arrival (when the message was originally put).   
       6. Committing and aborting messages for a UOW must be efficient.   

   SUMMARY OF THE INVENTION 
   The present invention contemplates extensions to the CF list architecture that allow MQSeries to efficiently exploit the CF list model and provide for shared queues in a Parallel Sysplex emvironment. The present invention is not limited to use in a message queueing environment, however, but may be used in other applications as well. 
   One aspect of the present invention contemplates a program-specified unique list entry identifier (ID) in place of the list entry ID generated by the system. In a parallel implementation of MQSeries, the CF list architecture should allow user-generated list entry identifiers to be used as a direct entry-locating mechanism in order to insure that the identifier for each list entry is unique across CF list structures and consistent between MQSeries queue managers. 
   MQSeries could accomplish this in the existing architecture by using list entry names. However, entry names and entry keys are mutually exclusive means of specifying list entries, and MQSeries also requires the use of entry keys for identifying list entries. MQSeries requires a function that is equivalent to that provided today by entry IDs as a direct means of addressing a list entry in a list structure. Currently, however, entry IDs are generated internally by the coupling facility. 
   In accordance with one aspect of the invention, a new list structure control—a program list entry identifier indicator, or PLEIDI—is defined to allow the user to specify whether user-defined entry IDs are used when the list is allocated. This new option is provided as an attribute of list structure allocation. 
   Corresponding modifications may be made to the operating system components that exploit the CF list architecture. Thus, in the case of the OS/390 component known as Sysplex Services for Data Sharing (XES), an optional input may be added to the XES Connection Service that indicates whether the user wishes to provide unique list entry ID values or the system should generate entry ID values for each list entry created for the structure. 
   A connect request is rejected if the connector&#39;s requested attribute does not match the attribute in effect for the current allocated instance of the structure. In a preferred embodiment, list entry ID type is consistent for a whole list structure. Either all list entries in the structure are referenced by entry IDs generated by the system, or all list entries are referenced by entry IDs provided by the user. 
   Another aspect of the present invention contemplates a new delete list (DL) command. MQSeries requires an efficient means to delete entries from a given list without knowledge of the specific list entry IDs of the entries to be deleted. In accordance with this aspect of the invention, a new delete list command is added that sequentially processes list entries in the order in which they exist on the specified list. The starting point for the list entry selection is specified by the head or tail of the list, entry ID, entry name, entry key, secondary key or list cursor. The new delete list command allows specific criteria to be specified that provides a means to target only particular entries to be processed for deletion. This command scans entries on a particular list and does not involve a scan of the entire structure. 
   The present invention also contemplates a new move list entries (MLES) command. A new command of this type is required by MQSeries to optimize the performance of two of their critical processes: committing MQPUT list entries and backing out of MQGET list entries. This requires updating each affected list entry, either by changing the list entry key while keeping the list entry on the same physical list in the CF list structure or by moving the list entry from one list back to its original list while the list entry key for the list entry remains unchanged. In accordance with this aspect of the invention, a new move list entries command has been added that provides a performance-optimized means to process an input list of entries. Each list entry in the input list may be moved to a new position on a list in the CF list structure by updating the list entry key, or each list entry may be moved from one list to another list in the coupling facility list structure by specifying a new target list number. The new move list entries command allows both the list number and the list entry key for a list entry to be updated. 
   The new move list entries (MLES) command is a multiple-list entry command, which takes as input a list of specified entries to be processed. The move list entries command takes a list of entries identified by list entry ID or name. For each entry in the input list a target list number, a target list entry key and a target secondary key may be provided. 
   In a preferred embodiment, a new input parameter—granular version number comparison (GVNC)—is provided on the move list entries (MLES) command to allow the user to optionally perform granular version number comparison. The move list entries command also allows granular version number replacement given the granular version number comparison was successful. A specified set of compare and replace criteria may be specified for each entry in the input entry list. 
   In a preferred embodiment, the input operand granular version number comparison (GVNC) is also added to the delete list entries (DLES) command to allow the user to optionally perform granular version number comparisons with a specified compare value criterion specified for each entry in the input entry list. Currently, the DLES command supports nongranular comparison functions, that is, comparison is performed between a single specified compare value and each of the entries in the input entry list. By adding the granular version number comparison to both DLES and MLES, the commands are kept consistent. However, the DLES command is preferably not changed to support version number replacement because version number replacement on a delete request is not supported by the architecture; updating an entry that will be deleted does not make sense. 
   In a preferred embodiment, another new operand—halt on miscompare (HOM)—is added to the move list entries (MLES) and delete list entries (DLES) commands to allow the user to specify whether execution should halt when a miscompare is encountered or continue to the next entry as is done currently. Miscompares may occur on the list entry version number, list entry key, list entry secondary key or list number. Currently, these commands skip an entry if a miscompare is encountered and continue processing with the next entry in the input list. This leads to the unfortunate circumstance that when any comparisons are requested, it is not possible for the user to determine which entries in the input entry list were deleted and which were skipped due to a miscompare because, upon completion the request only tells you how many entries were deleted. 
   Another aspect of the present invention contemplates key comparison enhancements to the CF list architecture. MQSeries uses entry keys and entry version numbers to identify the list entries by MQSeries queue manager and priority. To accomplish this, key comparison enhancements have been added for both single- and multiple-entry commands. The key compare functions that have been added are as follows:
     1. Location by keyed position has been enhanced to include operator types of range, less than or equal, and greater than or equal, for entry location of the first list entry to process on the read list (RL) and delete list (DL) commands.   2. For multiple-entry commands (i.e., commands for deleting, moving, reading and/or writing multiple list entries), the operands key request type (KRT), list entry key (LEK) and maximum list entry key (MLEK) (together with similar operands for the secondary keys described below) provide key comparison function operators of range, as well as key comparison function operators for less than or equal, and greater than or equal.   3. For single-list entry commands (i.e., commands for deleting, moving, reading and/or writing a single list entry), the operand key request type (KRT) (together with similar operands for the secondary keys described below) provides key comparison function operators of equal, less than or equal, and greater than or equal.   

   Yet another aspect of the present invention contemplates the following list monitoring enhancements:
     1. List monitoring for a key range or a “subset of sublists”.
       Currently, there are two levels of list notifications in the list model: (1) whole-list notification, to determine if the list is empty or not; and (2) sublist notification, to determine if the sublist defined by a list number and an entry key value is empty or not. This is not sufficient for MQSeries, which needs to be able to monitor lists with a granularity that lies between these two functions.   As described in the related application referenced above, MQSeries uses key values to group entries on a list into two ranges: committed entries and uncommitted entries. It would be desirable to know whether the set of committed entries on a list is empty or not, without actually having to access the CF to do so. To accomplish this, in a preferred embodiment, new list controls called key range (minimum) list entry key (KRLEK) and key range maximum list entry key (KRMLEK) are defined for each list to allow list monitoring to be set up for a range of keys. These list controls may be updated using the write list controls (WLC) command or read using the read list controls (RLC) command. Suitable means allow a user to start or stop monitoring the key range.   
       2. List and key range threshold notification.
       In a preferred embodiment, new list controls are added that allow the user to modify the list and key range empty-to-not-empty or not-empty-to-empty notification thresholds. These list controls, described below, may be updated using the write list controls (WLC) command.   The list empty notification threshold (LENT) is the number of list entries that must remain in the list to suppress a not-empty to empty list notification. The key range empty notification threshold (KRENT) is the number of list entries that must remain in the key range to suppress a not-empty to empty list notification A list or key range is considered empty when there are no entries on the list or when the list contains fewer list entries than the list or key range empty threshold. The list or key range may be considered empty even though there are still entries on the list or in the key range if the number of entries have not exceeded the list or key range empty threshold.   Similarly, the list not-empty notification threshold (LNENT) is the number of list entries that must be included in the list before an empty to not-empty list notification is generated, while the key range not-empty notification threshold (KRNENT) is the number of list entries that must be included in the key range before an empty to not-empty list notification is generated. A list or key range is considered not-empty when the number of list entries on the list is greater than the list or key range not-empty threshold. The list or key range may still be considered empty even there are entries on the list or in the key range, if the number of entries have not exceeded the list or key range not-empty count.   The initial value of the list and key range empty and not-empty thresholds is zero.   
       3. Aggressive sublist notification.
       In a preferred embodiment, a new event monitor control called an aggressive not-empty notification indicator (ANENI) is added to allow the user to specify whether, when monitoring a sublist, event monitor controls (EMCs) should be queued to the user&#39;s event queue for only the first entry added to the sublist or for each entry that is added to the sublist.   
       

   Yet another aspect of the present invention relates to keys. A new type of key, called a secondary key or, more particularly, a secondary list entry key (SLEK), is introduced that allows the user to specify a secondary key value as a means to identify a list entry. Secondary keys are associated with respective list entries and represent a second key ordering for each list in a CF list structure. A secondary key for an entry may be initialized, or set to null, when the entry is created. Secondary keys exist in parallel with primary keys and may be used and updated in a similar manner, as described below. In a preferred embodiment, a new list structure control called a secondary key indicator (SKI) is defined to allow for creation of secondary key control structures when the list is allocated. This allows the user to specify whether the keyed list structure should be allocated with only primary entry keys or with both primary and secondary entry keys. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a multiple-system complex (sysplex) incorporating the present invention. 
       FIG. 2  shows a put list associated with a particular shared queue, with committed and uncommitted portions. 
       FIG. 3  shows a get list associated with a particular shared queue manager. 
       FIG. 4  shows the format of a list entry key falling within the uncommitted key range. 
       FIG. 5  shows the format of a list entry key falling within the committed key range. 
       FIG. 6  shows the movement of list entries between the uncommitted and committed portions of a put list. 
       FIG. 7  shows the movement of list entries between a put list and a get list. 
       FIG. 8A  shows the procedure for writing a message to a queue. 
       FIG. 8B  shows the procedure for committing a write of a message to a queue. 
       FIG. 8C  shows the procedure for aborting a write of a message to a queue. 
       FIG. 8D  shows the procedure for reading (getting) a message from a queue. 
       FIG. 8E  shows the procedure for committing a read (get) of a message from a queue. 
       FIG. 8F  shows the procedure for aborting a read (get) of a message from a queue. 
       FIG. 9  shows the coupling facility and the list structures that it contains. 
       FIG. 10  shows a message command/response block. 
       FIG. 11  shows a list structure. 
       FIG. 12  shows a list. 
       FIG. 13A  shows a key range monitor table. 
       FIG. 13B  shows a list monitor table. 
       FIG. 13C  shows an event queue. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows the general configuration of a system complex (sysplex)  100  incorporating the present invention. Sysplex  100  comprises a plurality of systems  102  (an exemplary two of which, System A and System B, are shown), each of which is connected to a coupling facility (CF)  104  within which one or more shared message queues  106  are maintained. As is conventional, each system  102  comprises one or more processors and an operating system (not separately shown) and may constitute either a separate physical machine or a logical partition of a logically partitioned machine. Similarly, coupling facility  104  may constitute either a separate physical machine or a logical partition of a logically partitioned machine. Although the invention is not so limited, in a preferred embodiment the physical machines are IBM S/390 Parallel Enterprise Server® processors, while the operating system is the IBM OS/390® operating system. 
   Within each system  102 , user applications  110  perform sequences of operations, referred to herein as units of work (UOWs), on shared message queues  106  via a shared queue manager (SQM)  108  resident on that system. Shared queue managers  108  on different systems  102  that share the same message queue  106  are referred to herein as a queue-sharing group (QSG). In the preferred embodiment, each shared queue manager  108  in turn interacts with the coupling facility via a component  112  of the OS/390 operating system known as Sysplex Services for Data Sharing (XES). Sysplex Services for Data Sharing (XES) is described more fully in the IBM publication  MVS/ESA Programming: Sysplex Services Guide , GC28-1495-02 (June 1995), incorporated herein by reference. 
   User applications  110  on a system  102  interact with the shared queue manager  108  on that system via a series of Message Queue Interface (MQI) calls, the most important of which are MQPUT (to put a message onto a message queue  106 ) and MQGET (to get a message from a message queue  106 ). In response to such a call, shared queue manager  108  issues a call to XES  112  to invoke a requested system service (e.g., IXLLIST, IXLLSTC, IXLLSTE and IXLLSTM, as described below) to communicate with the coupling facility  104 . In response to receiving a call from shared queue manager  108 , XES  112  sends an appropriate message command block (MCB) containing data and other operands to the coupling facility  104  to perform the requested operation. XES  112  receives back from the coupling facility  104  a message response block (MRB) containing data and/or a response code. 
     FIG. 10  shows the format of a message command/response block  1000  used for communications between the coupling facility  104  and a particular system  102 . Message command/response block  1000  comprises a message command block (MCB)  1002 , a message response block (MRB)  1004 , and an optional data block  1006 . Message command block  1002  contains a command block  1008  and request operands  1010 . Similarly, message response block  1004  contains a response descriptor  1012  and response operands  1014 . Command block  1008  contains a command code (CC) specifying the type of operation to be performed by coupling facility  104 , while request operands  1010  constitute input parameters, as described below. 
   As part of its list-processing capability, coupling facility  104  performs requested operations on lists composed of one or more entries. Referring now to  FIGS. 2 and 3 , in accordance with one aspect of the present invention, each logical message queue  106  is implemented as a set of lists: a put list  202 , comprising a put list header (PLH) and optionally one or more list entries  204 , and one or more get lists  206 , each comprising a get list header (GLH) and optionally one or more list entries  204 . (The terms “list” and “list header” are used interchangeably herein in view of their one-to-one correspondence.) Each put list  202  is associated with a particular shared queue  106  and is shared by the shared queue managers  108  in the queue-sharing group. Each get list  206 , on the other hand, is associated with a particular shared queue manager  108  and may be used for multiple shared queues  106 . Each list entry  204  corresponds to a message. (The terms “list entry” and “message” are used interchangeably herein.) Associated with each list entry  204 , along with a message and other data, is a list entry key LEK that may be used to determine the order of the entry  204  in the list  202  or  206 . Keys LEK form the basis for partitioning the put list  202  into a committed portion  208 , in which the keys LEK fall within a committed key range, and an uncommitted portion  210 , in which the keys LEK fall within an uncommitted key range that does not overlap the committed key range. 
   Lists  202  and  206  and key ranges  208  and  210  supply the mechanism for writing, reading and committing messages  204  in accordance with the present invention. More particularly, the process of ‘hiding’ uncommitted messages  204 , hiding messages  204  that have been read and making committed puts globally visible is done simply by movement between list headers  202  and  206  and/or key assignment changes without the use of any explicit locking protocols. 
   The keys LEK that a list entry (message)  204  can be assigned are defined by the shared queue manager  108 , as described below. Referring to  FIGS. 4 and 8A , when a message  204  is initially put (step  802 ), it is first assigned the following 16-byte key LEK in the uncommitted key range (step  804 ):
         1 byte—value is X‘F6’   1 byte—queue manager ID (QMID) of the shared queue manager  108  that wrote the message  204     1 byte—priority of the message  204     8 bytes—UOW ID: 1-byte queue manager ID (QMID) concatenated with a 7-byte store clock (STCK) value   2 bytes—put list header (PLH): the list header  202  to which the message  204  was put   3 bytes—binary zeroes.       

   The set of list entries  204  whose key LEK begins with X‘F6’ define the uncommitted portion  210  of the (put) list header  202 . 
   Referring to  FIGS. 6 and 8B , when an uncommitted message  204  (first byte of key LEK is X‘F6’) is committed (step  806 ), it is moved from the uncommitted portion  210  of the list header  202  to the committed portion  208  of the same list header  202 . In this case, the list entry  204  moves from one position on the list header  202  to another position on the same list header  202 . The movement is accomplished by changing the list entry&#39;s key LEK so that it falls within the committed key range (step  808 ). Referring to  FIG. 5 , the uncommitted put key LEK is changed to the following:
         1 byte—priority in the inclusive range (0, 9)   8 byte—STCK value (from the uncommitted key, see above)   2 byte—put list header  202  (from the uncommitted key)   1 byte—queue manager ID (QMID) of the shared queue manager  108  that wrote the message  204     4 bytes—binary zeroes.       

   The set of list entries  204  whose keys begin with (00, 09) inclusive defines the committed portion  208  of the put list header  202 . 
   Referring to  FIG. 8C , if a unit of work decides to abort a write of a message  204  (step  810 ), it deletes the message  204  from the uncommitted portion  210  of the put list  202  (step  812 ). This portion  210  of the put list is available only to the unit of work that originally wrote the message  204  and is invisible to other units of work. 
   Referring to  FIGS. 7 and 8D , when a unit of work requests the highest committed message  204  on a get request (step  814 ), only the committed portion  208  of the list header  202  is eligible to be scanned, that is, list entries  202  whose keys begin with (00, 09) inclusive. Entries  204  that begin with X‘F6’ do not participate in the scan. 
   This is accomplished by using an IXLLSTE invocation (as described below) that examines the entry  204  at the head of the list  202  (step  816 ) and returns it only if the first byte of its key is in the inclusive range (00, 09). (This is referred to herein as key range checking on read.) If there are no messages  204  on the list header  202  or if the key of the message at the head of the list header begins with a value greater than or equal to X‘F6’ (step  818 ), then no message is returned (step  820 ). 
   If there are committed messages  204 , then the message  204  that is returned is the message at the head of the list header  202 , since the messages  202  are in priority order and within priority by time of arrival. Thus, if the message  204  at the head of the list  202  is a committed message (step  818 ), then two things happen in an atomic fashion:
     1. The contents of the list entry  204  are copied from the list structure into virtual storage (step  822 ).   2. The selected list entry  204  is moved to the ‘reading’ shared queue manager  108 &#39;s uncommitted get queue  206  (step  824 ). This move operation makes the message  204  invisible to all other shared queue managers  108  in the queue-sharing group who issue a get request to the corresponding PLH  202 . As noted earlier, in a list structure, each shared queue manager  108  is assigned its own uncommitted get list header  206 .   

   Once the message  204  is moved to the shared queue manager  108 &#39;s uncommitted get queue  206 , it is no longer visible to other get requests because all get requests for the shared queue  106  reference the shared queue&#39;s put list header  202 . 
   The final disposition of the message read will be either commit or abort. Referring to  FIG. 8E , if the disposition is commit (step  826 ), the message  204  is deleted from the shared queue manager  108 &#39;s uncommitted get queue  206  (step  828 ). Referring to  FIG. 8F , if the disposition is abort (step  830 ), then the message  204  is moved back to the committed put list header  202  from whence it came into its proper priority/time sequence position (step  832 ). 
   The list architecture of coupling facility  104 , insofar as it is pertinent to the present application, will now be described. 
   Referring to  FIG. 9 , coupling facility  104  contains microcode  904 , also referred to as coupling facility control code (CFCC), for managing one or more list structures  902 . Referring to  FIG. 11 , each list structure  902  contains a set of list structure controls  1102 , a list set  1104  comprising one or more lists  1106 , user controls  1108 , a lock table  1110  comprising one or more lock table entries (LTEs)  1112 , and one or more event queue controls  1114  and corresponding event queues  1116 . 
   Referring to  FIG. 12 , each list  1106  contains list controls  1202  (including a a key range monitor  110  table  1204  and a list monitor table  1206 ) and, optionally, one or more list entries  1208 . Each list entry  1208  in turn contains a set of list entry controls  1210  (including a list entry ID LEID and a list entry key LEK), a data list entry  1212  comprising one or more list elements (LEs)  1214 , and an adjunct list entry  1216  (including a secondary list entry key SLEK if defined). 
   List Structure Controls  1102   
   The fixed list structure controls  1102  are initialized when the list structure  902  is created and remain unchanged until it is deallocated. 
   The program-modifiable list structure controls  1102  are initialized when the list structure  902  is created. The program-modifiable control values may be changed by commands or CF processes. 
   The fixed list structure controls  1102  are summarized in the following table. 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               Fixed List Structure Controls 
               Acronym 
             
             
                 
                 
             
           
           
             
                 
               List count 
               LC 
             
             
                 
               List element characteristic 
               LELX 
             
             
                 
               List structure type 
               LST 
             
             
                 
               Maximum data list entry size 
               MDLES 
             
             
                 
               Maximum structure size 
               MXSS 
             
             
                 
                 
             
           
        
       
     
   
   The program-modifiable list structure controls  1102  are summarized in the following table. 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               Program-Modifiable List Structure Controls 
               Acronym 
             
             
                 
                 
             
           
           
             
                 
               Entry reapportionment-in-progress indicator 
               EREIPI 
             
             
                 
               Event monitor controls count 
               EMCC 
             
             
                 
               List set element count 
               LSELC 
             
             
                 
               List set entry count 
               LSEC 
             
             
                 
               Maximum event monitor controls count 
               MEMCC 
             
             
                 
               Maximum list set element count 
               MLSELC 
             
             
                 
               Maximum list set entry count 
               MLSEC 
             
             
                 
               Marginal structure size 
               MRSS 
             
             
                 
               Minimum apportionable structure size 
               MASS 
             
             
                 
               Pending entry-to-element ratio 
               PETELR 
             
             
                 
               Structure authority 
               SAU 
             
             
                 
               Structure size 
               SS 
             
             
                 
               Structure size change indicator 
               SSCI 
             
             
                 
               Target maximum element count 
               TMELC 
             
             
                 
               Target maximum entry count 
               TMEC 
             
             
                 
               Target maximum event monitor count 
               TMEMC 
             
             
                 
               Target structure size 
               TSS 
             
             
                 
               User identifier vector 
               UIDV 
             
             
                 
               User structure control 
               USC 
             
             
                 
                 
             
           
        
       
     
   
   Entry Reapportionment-in-Progress Indicator (EREIPI): Indicates whether an entry-to-element reapportionment process is currently active for the list structure  902 . 
   Event Monitor Controls Count (EMCC): Specifies the number of event monitor controls objects  1306  currently in a list set  1104 . 
   Extended User Structure Control (EUSC): An extension to the user structure control. 
   List Count (LC): Specifies the number of lists  1106  created. 
   List Element Characteristic (LELX): Specifies the number of bytes in each list element  1214 . 
   List Set Cursor (LSCUR): An integer that is either zero or contains the value of the current list number in the list set scan process. 
   List Set Element Count (LSELC): Specifies the number of list elements  1214  that have been assigned to list entries  1208  or retry-data blocks, or both, in the list set  1104 . 
   List Set Entry Count (LSEC): Specifies the number of existing list entries  1208  in the list set  1104 . 
   List Structure Type (LST): Indicates the list objects  1106  created on allocation. The first flag is a secondary key indicator (SKI), the second flag is a program list entry identifier indicator (PLEIDI), the third flag is a element count indicator (ECI), The fourth flag is a lock indicator (LI), the fifth flag is a data indicator (DI), the sixth flag is an adjunct indicator (AI), the seventh flag is a name indicator (NI), and the eighth flag is a key indicator (KI). 
   The secondary key indicator indicates whether secondary keys are supported. 
   The program list entry identifier indicator indicates whether the structure uses a coupling facility-assigned LEID value or a program-assigned LEID value. 
   The element count indicator indicates whether (1) list entry count and list entry count limit are defined or, alternatively, (2) list element count and list element count limit are defined. 
   The lock indicator indicates whether a lock table is created. 
   The data and adjunct indicators indicate respectively whether list entries have data entries and adjunct entries. 
   The name indicator indicates whether list entries are named. 
   The key indicator indicates whether list entries are keyed. 
   At least one of the lock, data or adjunct indicators is active (i.e., indicates that the condition is true). The name indicator and the key indicator are never both active. For the dequeue event monitor controls (DEMC), read event monitor controls (REMC), read event queue controls (REQC), and register event monitors (REMS) commands, the key indicator must be active; otherwise, the list structure type is invalid and a request exception is recognized. 
   Marginal Structure Size (MRSS): Specifies the minimum number of 4K-byte units of CF storage that are required for the creation of the requested lock table entries  1112 , lists  1106 , and associated controls for the list structure  902 , independent of either the storage increment size or the requested target entry-to-element ratio. 
   Maximum Data List Entry Size (MDLES): Specifies the maximum size of the data list entry  1212  as an integral multiple of the list element size. 
   Maximum Event Monitor Controls Count (MEMCC): Specifies the maximum number of possible event monitor controls objects  1306  in a list set  1104 . 
   Maximum List Set Element Count (MLSELC): Specifies the maximum number of list elements  1214  that are available for assignment to list entries  1208  or retry-data blocks, or both, in the list set  1104 . 
   Maximum List Set Entry Count (MLSEC): Specifies the maximum number of possible list entries  1208  in a list set  1104 . 
   Maximum Structure Size (MXSS): Specifies the maximum number of 4K-byte units of CF storage that can be allocated for the list  1106 . 
   Minimum Apportionable Structure Size (MASS): Specifies the minimum number of 4K-byte units of CF storage that can be allocated for the list  1106 , in integral multiples of the CF storage increment, that are sufficient for creating the requested lock table entries  1112 , lists  1106 , associated controls, enough event monitor controls  1306  and list entries  1208  with their associated controls to substantially satisfy the target monitor-to-entry storage ratio, and enough entries and elements to substantially satisfy the target entry-to-element ratio. 
   Monitor Reapportionment-in-Progress Indicator (MREIPI): Indicates whether a monitor-to-entry storage reapportionment process is currently active for the list structure  902 . 
   Pending Entry-to-Element Ratio (PETELR): Contains the last requested target entry-to-element ratio on an allocate list structure command. The PETELR object is updated when the list structure  902  is initially allocated and when a reapportionment process is initiated. 
   Pending Monitor-to-Entry Storage Ratio (PMTESR): Contains the last requested target monitor-to-entry storage ratio on an allocate list structure command. The PMTESR object is updated when the list structure  902  has been initially allocated and a monitor-to-entry storage reapportionment process is requested. 
   Reapportionment-in-Progress Indicator (REIPI): Indicates whether a reapportionment process is currently active for the list structure  902 . 
   Structure Authority (SAU): A value associated with each bit in the SID vector. 
   Structure Size (SS): Specifies the number of 4K-byte units allocated. 
   Structure Size Change Indicator (SSCI): Indicates whether an expansion or contraction process is currently active for the list structure  902 . 
   Target Maximum Element Count (TMELC): Specifies the target for the maximum number of list elements  1214  that are available for assignment to list entries  1208  or retry-data blocks, or both, in the list set  1104 . 
   Target Maximum Entry Count (TMEC): Specifies the target for the maximum number of possible list entries  1208  in a list set  1104 . 
   Target Maximum Event Monitor Count (TMEMC): Specifies the target for the maximum number of event monitor controls objects  1306  that are available for registration of interest in subsidiary lists within the list set  1104 . 
   Target Structure Size (TSS): Specifies the target number of 4K-byte units to be allocated. 
   User Identifier Vector (UIDV): A bit string with an initial value of zero. The bit positions start at zero and increase sequentially to the user identifier limit. The bit at position (i) in the string is set to one when a user is assigned with a UID value of (i). The bit at position (i) is reset to zero when a user is unassigned. 
   User Structure Control (USC): A field per structure defined by the user. 
   User Controls  1108   
   The user controls  1108  are created and initialized when a list structure user (such as a CF Manager component of shared queue manager  108 , as described below) is assigned and are deleted when the list structure user is unassigned.
         The user controls  1108  are summarized in the following table.       

   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               User Controls 
               Acronym 
             
             
                 
                 
             
           
           
             
                 
               List notification token 
               LNT 
             
             
                 
               System identifier 
               SYID 
             
             
                 
               User attachment control 
               UAC 
             
             
                 
               User authority 
               UAU 
             
             
                 
               User state 
               US 
             
             
                 
                 
             
           
        
       
     
   
   List Notification Token (LNT): Specifies a list notification vector to the system. 
   System Identifier (SYID): A value specified by the program when a message path is activated. The system identifier is maintained in the message path status vector and copied into the user controls  1108  when an attach list structure user command is communicated over the message path. 
   User Attachment Control (UAC): A field per attached user defined by the user. 
   User Authority (UAU): A value that is compared and conditionally updated. 
   User State (US): Specifies whether the user is attached. 
   Lock Table  1110   
   The lock table  1110  is a sequence of objects  1112 , called lock table entries. The number of lock table entries  1112  is determined when the table is created. The lock table entries  1112  are numbered from zero to the lock table entry count less one. 
   Each lock table entry  1112  has a global lock manager (GLM) object and an optional local lock managers (LLM) object. A lock table entry  1112  whose size is one byte has only a global lock manager object. When a lock table entry size is greater than one byte, the leftmost byte is the global lock manager object, and the remaining bytes form the local lock managers object. Lock tables  1110  with an entry size of one byte do not support local lock managers. Lock tables  1110  with an entry size of at least two bytes do support local lock managers. 
   The global lock manager object of a lock table entry  1112  contains an unsigned binary number called a user identifier. 
   The local lock managers object of a lock table entry  1112  contains a string of local lock bits, where each bit represents a user identifier. The bits in the object are numbered from left to right, starting at the value zero and proceeding upward to the bit for the highest valid user identifier. 
   The lock table objects have a value of zero when the table is allocated and may be modified by subsequent commands. 
   Event Queue Controls  1114   
   There is an event queue controls object  1114  for each event queue  1116  in a list structure  902 . All of the event queue controls of an event queue  1116  with the exception of the key type, are initialized to zero when the event queue  1116  is created or when the associated list structure user is detached. The key type is initialized to primary for the primary event queue controls and is initialized to secondary for the secondary event queue controls. 
   The event queue controls are summarized in the following table. 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               Event Queue Controls 
               Acronym 
             
             
                 
                 
             
           
           
             
                 
               Event monitor controls queued count 
               EMCQC 
             
             
                 
               Event notification entry number 
               ENEN 
             
             
                 
               Event notification request type 
               ENRT 
             
             
                 
               Event queue monitoring active bit 
               EQMAB 
             
             
                 
               Event queue transition count 
               EQTC 
             
             
                 
               Key type 
               KT 
             
             
                 
                 
             
           
        
       
     
   
   Event Monitor Controls Queued Count (EMCQC): Specifies the number of event monitor controls  1306  currently queued to the event queue  1116 . 
   Event Notification Entry Number (ENEN): Specifies a list notification vector entry associated with an event queue  1116 . 
   Event Notification Request Type (ENRT): Indicates whether the list notification vector summaries are to be updated when an empty to not-empty state transition occurs on an event queue  1116 . When active, this flag causes a user to be notified of empty-to-not empty transitions. 
   Event Queue Monitoring Active Bit (EQMAB): Specifies whether the user associated with the event queue  1116  is monitoring the event queue  1116 . 
   Event Queue Transition Count (EQTC): Specifies the number of empty to not-empty event queue transitions that have occurred. 
   Key Type (KT): Indicates the key type (primary or secondary) of the event monitor controls  1306  that are queued on the event queue  1116 . If the key type is primary, EMCs are queued for primary subsidiary lists; if the key type is secondary, EMCs are queued for secondary subsidiary lists. 
   Event Queue  1116   
   An event queue  1116  is a sequence of objects called event monitor controls  1306  (FIG.  13 C). There are zero, one, or two event queues  1116  created for each list structure user when the list structure  902  is allocated, depending on the list structure type. When the list structure  902  does not have keys, no event queues  1116  are created. When the list structure  902  has keys but not secondary keys, a single event queue  1116  is created for each user. This is referred to either as the event queue  1116  or the primary event queue  1116  When the list structure  902  has both keys and secondary keys, two event queues  1116  are created, a primary event queue  1116  that contains EMCs with list entry keys, and a secondary event queue  1116  that contains EMCs with secondary list entry keys. The event queues  1116  are deleted when the list structure  902  is deallocated. 
   An event monitor controls object  1306  is always queued to the rightmost position and dequeued from the leftmost position of the queue. 
   An event monitor controls object  1306  may be queued when (1) an empty to not-empty state transition occurs for a monitored subsidiary list, (2) notification of the initial subsidiary list state is requested on registration, or (3) a not-empty to not-empty state transition occurs for a monitored subsidiary list. An event monitor controls object  1306  may be withdrawn when a not-empty to empty state transition occurs for a monitored subsidiary list or when notification of the initial subsidiary list state is requested on registration, may be dequeued by means of the dequeue event monitor controls command, and may be deleted when a user deregisters interest in the subsidiary list or detaches from the list structure  902 . 
   List  1106   
   A list  1106  is a sequence of objects  1208 , called list entries. The number of possible entries  1208 , from one to 2 32 , is determined when the list structure  902  is created. 
   The relative position of a list entry  1208  in the sequence is determined when the entry is created and may be changed when any list entry  1208  is created, deleted, or moved. 
   A list entry  1208  is located by means of a list entry identifier, list entry name, or by position. List positions may be ordered by the time sequence of when list entries  1208  are created on or moved to a list  1106  or list positions may be in key order. There may be one or two key orderings for a list  1106 . If there is only one key ordering then list positions are ordered by increasing values of the list entry key. If two key orderings exist, then the primary key ordering is by increasing values of the list entry key and the secondary key ordering is by increasing values of the secondary list entry key. 
   The size of the largest list  1106  is limited by the free space and the size of all the controls required to support the list structure  902 . 
   A list entry  1208  has up to two objects: a data list entry  1212  and an adjunct list entry  1216 , depending on the list structure type. 
   A data list entry consists of from one to MDLES list elements  1214 . The data list entry size is determined when the data list entry is written. The list element size is a power of 2 that is at least 256 bytes. The adjunct list entry size is 64 bytes. 
   A list entry  1208  exists when it is created and ceases to exist when it is deleted. 
   Subsidiary List 
   A subsidiary list is a list within a list  1106  where all list entries  1208  have the same key. There are two types, depending on the type of key. Primary subsidiary lists consist of list entries  1208  on the same list  1106  with the same list entry key. Secondary subsidiary lists consist of all list entries  1208  on the same list  1106  with the same secondary list entry key. 
   A primary subsidiary list may only exist when a list set  1104  is created and the list entries  1208  are keyed. A secondary subsidiary list may only exist when a list set  1104  is created and secondary keys are supported in the structure. 
   Adjunct Data Entry 
   The adjunct data entry is a 64-byte storage object containing unformatted data. When the structure contains adjuncts and the adjunct format control bits in the list entry controls are inactive, the adjunct list entry is an adjunct data entry. 
   Adjunct Secondary Key Entry: The adjunct secondary key entry is a storage object containing the secondary list entry key and a secondary adjunct data area. When the structure contains secondary keys and the adjunct secondary key entry indicator in the adjunct format control is active, the adjunct list entry is an adjunct secondary key entry. 
   The adjunct secondary key entry objects are summarized in the following table. 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               Adjunct Secondary Key Entry 
               Acronym 
             
             
                 
                 
             
           
           
             
                 
               Secondary list entry key 
               SLEK 
             
             
                 
               Secondary adjunct data entry 
               SADE 
             
             
                 
                 
             
           
        
       
     
   
   Secondary List Entry Key (SLEK): Partially designates the position of the list entry  1208  in the list  1106  in secondary key order. 
   Secondary Adjunct Data Entry (SADE): A storage object containing unformatted data. 
   List Controls  1202   
   There is a list controls object  1202  for every list  1106  created in a list structure  902 . All the list controls  1202  except the list entry count limit and the list element count limit are initialized to zero when the list structure  902  is created. 
   The list controls  1202  are summarized in the following table. 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               List Controls 
               Acronym 
             
             
                 
                 
             
           
           
             
                 
               Assignment key 
               AK 
             
             
                 
               Assignment key threshold 
               AKT 
             
             
                 
               Cursor direction 
               CDIR 
             
             
                 
               Key range empty notification threshold 
               KRENT 
             
             
                 
               Key range list entry key 
               KRLEK 
             
             
                 
               Key range maximum list entry key 
               KRMLEK 
             
             
                 
               Key range monitor table 
               KRMT 
             
             
                 
               Key range not-empty notification threshold 
               KRNENT 
             
             
                 
               List authority 
               LAU 
             
             
                 
               List cursor 
               LCUR 
             
             
                 
               List element/list entry count 
               LELC/LEC 
             
             
                 
               List element count/list entry count limit 
               LELCL/LECL 
             
             
                 
               List empty notification threshold 
               LENT 
             
             
                 
               List monitor table 
               LMT 
             
             
                 
               List not-empty notification threshold 
               LNENT 
             
             
                 
               List state transition count 
               LSTC 
             
             
                 
                 
             
           
        
       
     
   
   Assignment Key (AK): Specifies the value assigned to a list entry key when a key assignment operation is executed for a list entry  1208  that is moved or created on the list  1106 . 
   Assignment Key Threshold (AKT): Specifies the maximum value of an assignment key. 
   Cursor Direction (CDIR): Indicates how the list cursor is updated (left to right or right to left) when the list cursor is maintained or initialized by a write list controls command. 
   Key Range Empty Notification Threshold (KRENT): Specifies a number which is one less than the number of list entries  1208  that must remain in the key range to suppress a not-empty-to-empty list notification. 
   Key Range List Entry Key (KRLEK): Specifies the lower value of the key range. 
   Key Range Maximum List Entry Key (KRMLEK): Specifies the upper value of the key range. 
   Key Range Not-empty Notification Threshold (KRNENT): Specifies one less than the number of list entries  1208  required in the key range in order to generate an empty-to-not-empty list notification. 
   List Authority (LAU): A value that is compared and conditionally updated. 
   List Cursor (LCUR): A list entry identifier that identifies a list cursor position. 
   List Element Count (LELC): Specifies the number of list elements  1214  currently in the list  1106 . 
   List Element Count Limit (LELCL): Specifies the maximum number of possible list elements  1214  in a list  1106 . 
   List Empty Notification Threshold (LENT): Specifies a number which is one less than the number of list entries  1208  that must remain in the list  1106  to suppress a not-empty-to-empty list notification. 
   List Not-empty Notification Threshold (LNENT): Specifies one less than the number of list entries  1208  required on the list  1106  in order to generate an empty-to-not-empty list notification. 
   List Entry Count (LEC): Specifies the number of list entries  1208  currently in the list  1106 . 
   List Entry Count Limit (LECL): Specifies the maximum number of possible list entries  1208  in a list  1106 . 
   Key Range Monitor Table  1204   
   The key range monitor table  1204  contains information used to process the list notification vector of each user who has registered interest in key range state transitions. 
   The key range monitor table  1204  is a sequence of objects  1302  (FIG.  13 A), called key range monitor table entries. The number of key range monitor table entries  1302  is determined when the table is created and is equal to the maximum number of list structure users plus one. The key range monitor table entries  1302  are numbered from zero to the user identifier limit. 
   Each key range monitor table entry  1302  has a key range monitoring active bit object, a key range notification request type object and key range notification entry number object. 
   Key Range Monitoring Active Bit (KRMAB): Specifies whether the user associated with the key range monitor table entry  1302  is monitoring the key range. 
   Key Range Notification Entry Number (KRNEN): Specifies a list notification vector entry associated with a monitored key range. 
   Key Range Notification Request Type (KRNRT): Indicates whether the list notification vector summaries are to be updated when an empty to not-empty state transition occurs on a monitored key range. When active, this flag causes the user to be notified of empty-to-not empty transitions. 
   Key range monitor table entry  1302   
                                           Key Range Monitor Table Entry Object   Acronym                           Key range monitor active bit   KRMAB           Key range notification request type   KRNRT           Key range notification entry number   KRNEN                        
List Monitor Table  1206   
   The list monitor table  1206  contains information used to process the list notification vector of each user who has registered interest in the state transitions of the list  1106 . 
   The list monitor table  1206  is a sequence of objects  1304  (FIG.  13 B), called list monitor table entries. The number of list monitor table entries  1304  is determined when the table is created and is equal to the maximum number of list structure users plus one. 
   The list monitor table entries  1304  are numbered from zero to the user identifier limit. 
   Each list monitor table entry  1304  has a list monitoring active bit object, a list notification request type object and a list notification entry number object. 
   List Monitoring Active Bit (LMAB): Specifies whether the user associated with the list monitor table entry  1304  is monitoring the list. 
   List Notification Entry Number (LNEN): Specifies a list notification vector entry associated with a monitored list  1106 . 
   List Notification Request Type (LNRT): Indicates whether the list notification vector summaries are to be updated when an empty to not-empty state transition occurs on a monitored list  1106 . 
   List Monitor Table Entry 
                                           List Monitor Table Entry Object   Acronym                           List monitor active bit   LMAB           List notification request type   LNRT           List notification entry number   LNEN                        
List Entry Controls  1210   
   There is a list entry controls object  1210  for every list entry  1208  within a structure. The list entry controls  1210  are initialized when a list entry  1208  is created and are deleted when a list entry  1208  is deleted. The list entry controls  1210  are summarized in the following table. 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               List Entry Controls 
               Acronym 
             
             
                 
                 
             
           
           
             
                 
               Adjunct format control 
               AFC 
             
             
                 
               Data-list-entry size 
               DLES 
             
             
                 
               List entry identifier 
               LEID 
             
             
                 
               List entry key 
               LEK 
             
             
                 
               List number 
               LN 
             
             
                 
               Version number 
               VN 
             
             
                 
               Adjunct data entry 
               ADE 
             
             
                 
                 
             
           
        
       
     
   
   Adjunct Format Control (AFC): A bit string consisting of adjunct format bits. Each bit is associated with a particular adjunct format. The adjunct format control bits include an adjunct secondary key entry indicator and (2) an adjunct lock entry indicator. The bits are mutually exclusive; at most one bit is active. When all the bits are inactive, the adjunct list entry  1216  is unformatted and contains the adjunct data entry. 
   Data List Entry Size (DLES): Specifies the size of the data list entry  1212  as an integral multiple of the list element size. 
   List Entry Identifier (LEID): Designates the list entry  1208 . 
   List Entry Key (LEK): Partially designates the position of the list entry  1208  in the list  1106 . 
   List Number (LN): Designates the list  1106  that the list entry  1208  is in. 
   Event Monitor Controls  1306   
   There is an event monitor controls object  1306  for every user and subsidiary list combination for which a user has currently registered interest. The number of possible event monitor controls  1306 , from one to 2 32 −1, is determined when the list structure  902  is created and may be changed when structure storage is expanded or contracted or the monitor-to-entry storage ratio is reapportioned. 
   An event monitor controls object  1306  is created when a user initially registers interest and is deleted when a user deregisters interest in a subsidiary list or detaches from the list structure  902 . 
   All the event monitor controls  1306  except the event monitor queued indicator are initialized to the values provided as request operands  1010  during registration. 
   The event monitor controls  1306  are summarized in the following table. 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               Event Monitor Controls 
               Acronym 
             
             
                 
                 
             
           
           
             
                 
               Aggressive not-empty notification indicator 
               ANENI 
             
             
                 
               Event monitor queued indicator 
               EMQI 
             
             
                 
               List entry key/Secondary list entry key 
               LEK/SLEK 
             
             
                 
               List number 
               LN 
             
             
                 
               Key type 
               KT 
             
             
                 
               User identifier 
               UID 
             
             
                 
               User notification control 
               UNC 
             
             
                 
                 
             
           
        
       
     
   
   Aggressive Not-empty Notification Indicator (ANENI): When inactive, indicates that the event monitor controls  1306  should be queued to the event queue  1116  for only the first list entry  1208  added to a subsidiary list. When active, indicates that the event monitor controls  1306  should be queued to the event queue for every list entry  1208  that is added. 
   Event Monitor Queued Indicator (EMQI): Indicates whether the event monitor controls object  1306  is queued to the event queue  1116  associated with the user ID contained within the object. 
   List Entry Key (LEK): Partially designates the primary subsidiary list. 
   List Number (LN): Partially designates the subsidiary list. 
   Key Type (KT): Indicates the key type (primary or secondary) in the event monitor controls  1306 . When the key type is primary, the key is a (primary) list entry key and the event monitor controls  1306  are associated with a primary subsidiary list. When the key type is secondary, the key is a secondary list entry key and the event monitor controls  1306  are associated with a secondary subsidiary list. 
   Secondary List Entry Key (SLEK): Partially designates the secondary subsidiary list. 
   User Identifier (UID): Identifies the user. 
   User Notification Control (UNC): A field per event monitor controls  1306  defined by the user. 
   List Structure Object States 
   List States 
   A list  1106  is either in the empty or the not-empty state. 
   Empty State: A list  1106  is in the empty state when the number of list entries  1208  on the list  1106  is less than or equal to the list empty notification threshold. 
   Not-empty State: A list  1106  is in the not-empty state when the number of entries on the list  1106  is greater than the list not-empty notification threshold. 
   When the empty and not-empty notification thresholds for the list  1106  are not equal and the number of entries on the list  1106  falls between the list empty notification threshold and the list not-empty notification threshold, inclusive of the latter, the state of the list  1106  is determined as follows:
     1. If an empty-to-not-empty list notification has not been generated since the list  1106  was created, the list  1106  is in the empty state.   2. If an empty-to-not-empty list notification has been generated since the list  1106  was created, the state of the list  1106  depends on the last generated list notification; if the last generated list notification is an empty-to-not-empty transition, the state of the list  1106  is not empty, otherwise the list  1106  is empty.
 
List State Transitions
   

   A user may register interest in the state transitions of a list  1106  by means of the register list monitor command. A list  1106  may change either from the not-empty to the empty state or from the empty to the not-empty state. 
   Empty to Not-empty List State Transition: A list  1106  that is in the empty state changes from the empty to the not-empty state when an entry is created on or moved to the list  1106  and the number of list entries  1208  on the list  1106  becomes one greater than the list not-empty notification threshold. 
   Not-empty to Empty List State Transition: A list  1106  that is in the not empty state changes from the not-empty to the empty state when an entry is deleted from the list  1106  or moved to another list  1106  and the number of list entries  1208  on the list  1106  becomes equal to the list empty notification threshold. 
   Key Range States 
   A key range is either in the empty or the not-empty state. A user may request a notification of the initial state of a key range by means of the initial notification request type on the register list monitor command. 
   Empty State: A key range is in the empty state when the number of list entries  1208  in the key range is less than or equal to the key range empty notification threshold. 
   Not-empty State: A key range is in the not-empty state when the number of entries in the key range is greater than the key range not-empty notification threshold. 
   When the empty and not-empty notification thresholds for the key range are not equal and the number of entries in the key range falls between the key range empty notification threshold and the key range not-empty notification threshold, inclusive of the latter, the state of the key range is determined as follows:
     1. If an empty-to-not-empty list notification has not been generated since the key range was initialized, the key range is in the empty state.   2. If an empty-to-not-empty list notification has been generated since the key range was initialized, the state of the key range depends on the last generated list notification; if the last generated list notification is an empty-to-not-empty transition, the state of the key range is not empty, otherwise the key range is empty.
 
Key Range State Transitions
   

   A user may register interest in the state transitions of a key range by means of the register list monitor command. A key range may change either from the not-empty to the empty state or from the empty to the not-empty state. 
   Empty to Not-empty Key Range State Transition: A key range that is in the empty state changes from the empty to the not-empty state when (1) an entry is created in the key range, (2) an entry is moved to the key range, or (3) key range initialization completes, and the number of list entries  1208  in the key range becomes greater than the key range not-empty notification threshold when the number had previously been less than or equal to the threshold. 
   Not-empty to Empty Key Range State Transition: A key range that is in the not empty state changes from the not-empty to the empty state when an entry is (1) deleted from the key range, (2) moved to another list  1106 , (3) moved to the same list  1106  with a new list entry key that is outside of the key range, or (4) key range initialization completes, and the number of list entries  1208  in the key range becomes less than or equal to the key range empty notification threshold when the number had previously been greater than the threshold. 
   Subsidiary List States 
   A subsidiary list is either in the empty or the not-empty state. A user may request to queue or withdraw the event monitor controls object  1306  to reflect the initial state of a subsidiary list by means of the initial notification request type on the register list monitor or register event monitors command. 
   Empty State: A subsidiary list is in the empty state when there are no entries in the subsidiary list. 
   Not-empty State: A subsidiary list is in the not-empty state when there are one or more entries in the subsidiary list. 
   Subsidiary List State Transitions 
   A user may register interest in the state transitions of a subsidiary list by means of the register list monitor or register event monitors command. 
   A subsidiary list may change either from the not-empty to the empty state, from the empty to the not empty state, or from the not-empty to the not-empty state. 
   Empty to Not-empty Subsidiary List State Transition: A subsidiary list changes from the empty to the not-empty state when the subsidiary list has no entries and an entry is created or moved to the subsidiary list. 
   Not-empty to Empty Subsidiary List State Transition: A subsidiary list changes from the not-empty to the empty state when the subsidiary list has one entry and the entry is deleted or moved to another subsidiary list. 
   Not-empty to Not-empty Subsidiary List State Transition: A subsidiary list changes from the not-empty to the not-empty state when (1) the subsidiary list is not empty, (2) an entry is created or moved to the subsidiary list, (3) the event monitor queued indicator is active and the aggressive not-empty notification indicator is active in the associated EMC. 
   Event Queue States 
   An event queue  1116  is either in the empty or the not-empty state. A user may request a notification of the initial state of an event queue  1116  by means of the initial notification request type on the register list monitor command. 
   Empty State: An event queue  1116  is in the empty state when there is no event monitor controls object  1306  queued to the event queue  1116 . 
   Not-empty State: An event queue  1116  is in the not-empty state when there are one or more event monitor controls objects  1306  queued to the event queue  1116 . 
   Event Queue State Transitions 
   A user may register interest in the state transitions of an event queue  1116  by means of the register list monitor command. An event queue  1116  may change either from the not-empty to the empty state or from the empty to the not-empty state. 
   Empty to Not-empty Event Queue State Transition: An event queue  1116  changes from the empty to the not-empty state when the event queue  1116  has no queued object and an event monitor controls object  1306  is queued to the event queue  1116 . 
   Not-empty to Empty Event Queue State Transition: An event queue  1116  changes from the not-empty to the empty state when the event queue  1116  has one event monitor controls object  1306  queued and the object is dequeued, withdrawn, or deleted. 
   Creating a List Structure 
   When a list structure  902  is created, the list structure type determines the attributes of the created structure. The list structure type has indicators for each of the following: program list entry identifier indicator, counters, locks, data, adjunct, name, key, and secondary key. 
   When the program list entry identifier indicator in the list structure type specified is inactive and allocation is successful, the list structure  902  uses list entry identifier values that are generated by the coupling facility. 
   When the program list entry identifier indicator in the list structure type specified is active and allocation is successful, the list structure  902  uses list entry identifier values that ate program assigned. 
   When the element count indicator in the list structure type specified is inactive and allocation is successful, the list controls  1202  for each list  1106  contain a list entry count and a list entry count limit. When the count indicator in the list structure type specified is active and allocation is successful, the list controls  1202  for each list  1106  contain a list element count and a list element count limit. 
   When the lock indicator in the list structure type specified is active and allocation is successful, a lock table  1110  is created with a width as specified by the lock table entry characteristic and a length as specified by the lock table entry count. 
   When the data indicator in the list structure type specified is active and allocation is successful, storage is allocated for the creation of list elements  1214 . The size of the list elements  1214  is specified by the list element characteristic. 
   When the adjunct indicator in the list structure type specified is active and allocation is successful, each list entry  1208  created in the structure has an adjunct list entry  1216  with a size of 64 bytes. 
   When the name indicator in the list structure type specified is active and allocation is successful, each list entry  1208  created in the structure has a list entry name associated with it. 
   When the key indicator in the list structure type specified is active and allocation is successful, every user identifier has primary event queue controls associated with it, each list entry  1208  created in the structure has a list entry key associated with it, and each list  1106  has a key range associated with it. The key range list entry key and maximum key range list entry key are both set to zero, and the key range is placed in the empty state. 
   When the secondary key indicator in the list structure type specified is active and allocation is successful, every user identifier has secondary event queue controls associated with it and each list entry  1208  created in the structure has a secondary list entry key associated with it stored in the adjunct list entry  1216 . 
   When a list structure  902  is created, (1) the free space and free control space global controls are updated, (2) the appropriate created bit in the structure identifier vector is set to one, and (3) the list structure and list controls  1202  are initialized, including the update of the target structure size and target count objects. 
   When a list structure  902  is created and the maximum structure size request operand  1010  is nonzero, the maximum structure size object is initialized to the largest storage size that the model can support given the structure size and is equal to or smaller than the maximum structure size request operand  1010  rounded up to the nearest integral multiple of the CF storage increment. 
   When a list structure  902  is created, target structure size request operand  1010  is zero, and the maximum structure size request operand  1010  is zero, the maximum structure size object is set equal to the computed target structure size. 
   Specifying a nonzero target structure size which is smaller than the marginal structure size or larger than the maximum structure size will cause the allocation to complete with an appropriate response code. 
   Comparing List Authorities 
   The list authorities are always compared when the write list controls command is executed. Otherwise, the comparison of list authorities is controlled by the list authority comparison type operand. When the value of the list authority comparison type is do not compare, the list authorities are not compared and list authority comparison is successful. 
   When the value of the list authority comparison type is compare for being equal or compare for being less than or equal or when a write list controls command is executed, the CLAU operand is compared with the value of the list authority control in the specified list  1106 . 
   The specified list  1106  is designated by the LN operand  1010  in the MCB  1002 . The only exception is that when the write and move list entry command results in the creation of a list entry  1208 , the specified list  1106  is designated by the TLN operand  1010  in the MCB  1002 . 
   When the value of the list authority comparison type is compare for being equal and they are equal, the list authority comparison succeeds, and the command continues. 
   When the value of the list authority comparison type is compare for being less than or equal and the list authority control is less than or equal to the CLAU operand, the list authority comparison succeeds and the command continues. 
   When the list authority comparison fails, command execution is completed with an appropriate response code. 
   Replacing List Authorities 
   The list authority control may be replaced when the write list controls command is executed. Otherwise, the replacement of list authorities is controlled by the list authority replacement type and list authority comparison type operands. When the value of the list authority replacement type is active, the value of the LAU operand is stored in the list authority control provided one of the following conditions exists: 
   The command is write list controls and list authority comparison is successful, and (1) The value of the LAUCT operand is do not compare, or (2) The value of the LAUCT operand is compare for being equal or compare for being less than or equal and list authority comparison is successful. 
   List authority comparison always occurs before any list objects are updated. 
   Comparing Keys 
   When the key comparison type is active, the list entry key object is compared with the list entry key request operand  1010  and optionally the maximum list entry key operand. The key request type operand specifies how the keys are compared. 
   When the secondary key comparison type is active, the secondary list entry key object is compared with the secondary list entry key request operand  1010  and optionally the maximum secondary list entry key operand. The secondary key request type operand specifies how the keys are compared. 
   When both the key comparison type and the secondary key comparison type are active, both key comparisons are performed and both must succeed in order for the key comparison to be successful. 
   For multiple list entry commands, the key comparison is on an entry basis, the key is compared for the entry and the delete, read, or move for the entry occurs if the key comparison is successful for the entry. When the comparison is successful, the list entry  1208  is selectable by a multiple list entry command. When the comparison is unsuccessful, the list entry  1208  is not selectable. 
   Initializing a Key Range 
   A key range is initialized when a write list controls command is executed and the key range list entry key and key range maximum list entry key are updated or when a list  1106  is created and the list  1106  is keyed. A key range is initialized by calculating the number of list entries  1208  in the key range, comparing the count to the key range threshold values, and setting the key range state to either the empty state or the not-empty state. Initialization of the key range can be continued or completed by either continued executions of the write list controls command with bit  7  of the LCT active or by continued execution of the register list monitor command with a monitor request type of key range monitor. If key range initialization is not complete, the WLC or RLM commands complete with appropriate response codes. 
   If key range initialization is not complete, and a WLC command is executed with bit  7  of the LCT inactive or a RLM command is executed and the monitor request type is not key range monitor, then the WLC and RLM commands are executed independently from key range initialization. 
   If the WLC command is executed with bit  7  of the LCT active, key range initialization is in progress, and the specified key range list entry key or key range maximum list entry key are different from the values associated with the key range, initialization of the prior key range is stopped and initialization of the new key range is started. 
   Comparing Global Lock Managers 
   Generally, a global lock manager comparison is performed before a lock table entry  1112  is written, and a global lock manager comparison may be performed before the next nonzero lock table entry  1112  is read, or before a list entry  1208  is created, replaced, read, moved, or deleted, or before an adjunct lock entry is updated by an adjunct locking operation. 
   The global lock manager object is compared with the comparative global lock manager specified. When they match, the global lock manager comparison succeeds. When they do not match, the global lock manager comparison fails. 
   Except for the reset lock managers command and the read next lock table entry command, when a lock table write is to be performed, when a list entry creation, replacement, read, movement, or deletion is to be performed, or when an adjunct lock entry is to be updated by an adjunct locking operation, if the global lock manager comparison is requested and succeeds, the command continues; if the global lock manager comparison is requested and fails, command execution is completed with an appropriate response code. 
   For the reset lock managers command with the unlock type operand set to either B‘10’ or B‘11’, if the global lock manager comparison succeeds, the command continues. If the global lock manager comparison fails and if the report mismatch type operand is B‘0’, then a lock manager mismatch response code is returned. If the global lock manager comparison fails and if the report mismatch type operand is B‘1’, then the current request block is skipped and the command continues to process the next request block. 
   For the reset lock managers command with the unlock type operand set to B‘01’, if the global lock manager comparison succeeds and the report mismatch type operand is B‘1’, or both global and local lock manager comparisons are successful, the command continues. If the global lock manager comparison or local lock manager comparison fails, and the report mismatch type operand is B‘0’, then a lock manager mismatch response code is returned. If the global lock manager comparison fails and if the report mismatch type operand is B‘1’, then the current request block is skipped and the command continues to process the next request block. 
   For the read next lock table entry command with the lock request type operand set to compare global lock managers, if the global lock manager comparison succeeds on a nonzero lock table entry  1112 , the entry is returned; if the global lock manager comparison fails, the entry is skipped and the scan of the lock table  1110  continues. 
   For the read next lock table entry command with the lock request type operand set to compare global lock or local lock managers, if either global lock manager or local lock manager comparison succeeds on a nonzero lock table entry  1112 , the entry is returned; if neither comparison succeeds, the entry is skipped and the scan of the lock table  1110  continues. 
   Comparing Local Lock Managers 
   Generally, local lock manager comparison may occur before a lock table entry  1112  is written, before an adjunct lock entry is updated by an adjunct locking operation, before the next nonzero lock table entry  1112  is read, or before a list entry  1208  is created, replaced, read, moved, or deleted. 
   Local lock manager comparison is also performed as part of the global lock manager replacement process, and may also be performed as part of the local lock manager replacement process. 
   When a local lock manager object exists and a global lock manager replacement is requested, the local lock manager object value is ANDed with a mask of all ones except for the local lock bit corresponding to the user identifier specified. This ANDed value is then compared with zero. When they match, the local lock manager comparison succeeds. When they do not match, the local lock manager comparison fails. 
   When a local lock manager object exists and a local lock manager comparison is requested, or when a local lock manager object exists and a local lock manager replacement that requires the local lock manager comparison to be performed, is requested, the local lock bit corresponding to the user identifier specified is compared with the local lock bit value specified. When (1) they match and local lock manager comparison is requested or (2) they do not match and local lock manager replacement is requested, the local lock manager comparison succeeds. When (1) they do not match and local lock manager comparison is requested or (2) they match and local lock manager replacement is requested, the local lock manager comparison fails. 
   Except for the reset lock managers command and the read next lock table entry command, when a lock table write is to be performed, when a list entry creation, replacement, read, movement, or deletion is to be performed, or when an adjunct lock entry is to be updated by an adjunct locking operation, if the local lock manager comparison is requested and succeeds, the command continues; if the local lock manager comparison is requested and fails, command execution is completed with an appropriate response code. 
   For the reset lock managers command, local lock manager comparison may be performed when the unlock type operand is B‘01’. In this case, if the global lock manager comparison succeeds and the report mismatch type operand is B‘1’, or both global and local lock manager comparisons are successful, the command continues. If the global lock manager comparison or local lock manager comparison fails, and the report mismatch type operand is B‘0’, then a lock manager mismatch response code is returned. 
   For the read next lock table entry command with the lock request type operand set to compare local lock managers, if the local lock manager comparison succeeds on a nonzero lock table entry  1112 , the entry is returned; if the local lock manager comparison fails, the entry is skipped and the scan of the lock table  1110  continues. 
   For the read next lock table entry command with the lock request type operand set to compare global lock or local lock managers, if either global lock manager or local lock manager comparison succeeds on a nonzero lock table entry  1112 , the entry is returned; if neither comparison succeeds, the entry is skipped and the scan of the lock table  1110  continues. 
   Locating a List Entry or List Entry Position 
   A list entry  1208  is located by unkeyed position. when an entry locator type of locate by unkeyed position is specified or an unkeyed list entry  1208  is created or moved; that is, the designated position or designated target position is specified by means of a list number and a direction. 
   A list entry  1208  is located by keyed position when the list entries  1208  are keyed and an entry locator type of locate by keyed position is specified or a keyed list entry  1208  is created or moved; that is, the designated position or designated target position is specified by means of a list number, direction, and a list entry key. 
   A list entry  1208  is located by list entry identifier when an entry locator type of locate by list entry identifier is specified; that is, the designated position is the position of the identified list entry  1208 . 
   A list entry  1208  is located by list entry name when the list entries  1208  are named and an entry locator type of locate by list entry name is specified; that is, the designated position is the position of the named list entry  1208 . 
   A list entry  1208  is located by list cursor position when an entry locator type of locate by list cursor position is specified; that is the designated position is the position of the identified list entry  1208  as specified by the list cursor. 
   A list entry  1208  has a position relative to the designated position or the designated target position. When a list entry  1208  is created, moved, or deleted, the relative positions of the successive list entries  1208  are changed. In these cases, the first entry is the designated list entry  1208  and successive entries are determined by the direction specified. 
   Regardless of how a list entry  1208  is located, when a left-to-right direction is specified, the last entry is the rightmost entry in the list  1106 , and when a right-to-left direction is specified, the last entry is the leftmost entry in the list  1106 . 
   Designated List Entry 
   The designated list entry  1208  is (1) the first entry relative to the designated position before an entry is deleted, moved, read, replaced, replaced and moved, moved and read, or read and deleted, or is (2) the first entry relative to the designated target position after an entry is created. 
   When a list entry  1208  is located by list entry identifier, the designated list entry  1208  is the identified list entry  1208 . 
   When a list entry  1208  is located by list entry name, the designated list entry  1208  is the named list entry  1208 . 
   When a list entry  1208  is located by list cursor position, the designated list entry  1208  is the identified list entry  1208  as specified by the list cursor. 
   When a list entry  1208  is located by unkeyed position and a left-to-right direction is specified, the designated list entry  1208  is the leftmost entry in the list  1106 . When a list entry  1208  is located by unkeyed position and a right-to-left direction is specified, the designated list entry  1208  is the rightmost entry in the list  1106 . 
   When (1) a list entry  1208  is located by keyed position the entry locator key type is primary, and the KRT does not indicate key range, (2) entry deletion, read, replacement, or movement is requested, (3) a list entry  1208  with an equal key, a less than or equal key, or a greater than or equal key, exists on the list  1106 , depending on the key request type, and (4) a left-to-right direction is specified, then the designated list entry  1208  is the leftmost entry with a key equal, with the largest key less than or equal, or with the smallest key greater than or equal to the specified list entry key request operand  1010 .
         When (1) a list entry  1208  is located by keyed position, the entry locator key type is primary, and the KRT does not indicate key range, (2) entry deletion, read, replacement, or movement is requested, (3) a list entry  1208  with an equal key, a less than or equal key, or a greater than or equal key, exists on the list  1106 , depending on the key request type, and (4) a right-to-left direction is specified, then the designated list entry  1208  is the rightmost entry with a key equal, with the largest key less than or equal, or with the smallest key greater than or equal to the specified list entry key request operand  1010 .   When (1) a list entry  1208  is located by keyed position, the entry locator key type is secondary, and the SKRT does not indicate key range, (2) entry deletion, read, replacement, or movement is requested, (3) a list entry  1208  with an equal secondary key, a less than or equal secondary key, or a greater than or equal secondary key, exists on the list  1106 , depending on the secondary key request type, and (4) a left-to-right direction is specified, then the designated list entry  1208  is the leftmost entry with a secondary key equal, with the largest secondary key less than or equal, or with the smallest secondary key greater than or equal to the specified secondary list entry key request operand  1010 .       

   When (1) a list entry  1208  is located by keyed position, the entry locator key type is secondary, and the SKRT does not indicate key range, (2) entry deletion, read, replacement, or movement is requested, (3) a list entry  1208  with an equal secondary key, a less than or equal secondary key, or a greater than or equal secondary key, exists on the list  1106 , depending on the secondary key request type, and (4) a right-to-left direction is specified, then the designated list entry  1208  is the rightmost entry with a secondary key equal, with the largest secondary key less than or equal, or with the smallest secondary key greater than or equal to the specified secondary list entry key request operand  1010 . 
   When (1) a list entry  1208  is located by keyed position, the entry locator key type is primary, and the KRT indicates key range, (2) entry deletion, read, replacement, or movement is requested, (3) a list entry  1208  with a key within range exists on the list  1106 , and (4) a left-to-right direction is specified, then the designated list entry  1208  is the leftmost entry with a key value greater than or equal to the specified list entry key request operand  1010 . 
   When (1) a list entry  1208  is located by keyed position, the entry locator key type is primary, and the KRT indicates key range, (2) entry deletion, read, replacement, or movement is requested, (3) a list entry  1208  with a key within range exists on the list  1106 , and (4) a right-to-left direction is specified, then the designated list entry  1208  is the rightmost entry with a key value less than or equal to the specified maximum list entry key request operand  1010 . 
   When (1) a list entry  1208  is located by keyed position, the entry locator key type is secondary, and the SKRT indicates key range, (2) entry deletion, read, replacement, or movement is requested, (3) a list entry  1208  with a secondary key within range exists on the list  1106 , and (4) a left-to-right direction is specified, then the designated list entry  1208  is the leftmost entry with a secondary key value greater than or equal to the specified secondary list entry key request operand  1010 . 
   When (1) a list entry  1208  is located by keyed position, the entry locator key type is secondary, and the SKRT indicates key range, (2) entry deletion, read, replacement, or movement is requested, (3) a list entry  1208  with a secondary key within range exists on the list  1106 , and (4) a right-to-left direction is specified, then the designated list entry  1208  is the rightmost entry with a key value less than or equal to the specified maximum secondary list entry key request operand  1010 . 
   Designated Position 
   The designated position is the position of the designated list entry  1208  before an entry is moved, deleted, read, replaced, replaced and moved, moved and read, or read and deleted. 
   The designated position is specified (1) by an unkeyed position, (2) by a keyed position, (3) by a list entry identifier, (4) by a list entry name, or (5) by a list cursor, depending on the entry locator type and the entry locator key type specified and the type of structure allocated. 
   When a list entry  1208  is located by list entry identifier or by list entry name, the designated position exists when the list entry  1208  exists. 
   When a list entry  1208  is located by list cursor, the designated position exists when the identified list entry  1208  exists as specified by the list cursor. 
   When a list entry  1208  is located by unkeyed position, the designated position exists when the list  1106  exists and there is at least one entry on the list  1106 . 
   When a list entry  1208  is located by keyed position and entry creation is not requested, the designated position exists when a list entry  1208  in the list  1106  has a key that is equal, greater than or equal, or less than or equal to the specified list entry key in the list  1106 , depending on the key request type. 
   When a list entry  1208  is located by keyed position, the entry locator key type is primary, and entry creation is not requested, the designated position exists when a list entry  1208  in the list  1106  has a key that is equal to, greater than or equal to, less than or equal to, or within the range specified by the list entry key and the maximum list entry operands, depending on the key request type. 
   When a list entry  1208  is located by keyed position, the entry locator key type is secondary, and entry creation is not requested, the designated position exists when a list entry  1208  in the list  1106  has a secondary key that is equal to, greater than or equal to, less than or equal to, or within the range specified by the secondary list entry key and the maximum secondary list entry operands, depending on the secondary key request type. 
   When the designated position does not exist, an appropriate response code is returned. 
   Designated Target Position 
   The designated target position is the position of the designated list entry  1208  after an entry is created or moved. 
   The designated target position is specified (1) by an unkeyed position or (2) by a keyed position, depending on the type of structure allocated. 
   When a list entry  1208  is located by unkeyed position and a left-to-right direction is specified, then the designated target position is the leftmost position in the list  1106 . When a list entry  1208  is located by unkeyed position and a right-to-left direction is specified, then the designated target position is the rightmost position in the list  1106 . 
   When (1) a list entry  1208  is located by keyed position, (2) entry creation or movement is requested, (3) a list entry  1208  with an equal key of the specified entry locator key type exists on the list  1106 , (4) a left-to-right direction is specified, then the designated target position is the position of the leftmost entry with the same key. 
   When (1) a list entry  1208  is located by keyed position, (2) entry creation or movement is requested, (3) a list entry  1208  with an equal key of the specified entry locator key type exists on the list  1106 , (4) a right-to-left direction is specified, then the designated target position is the position of the rightmost entry with the same key. 
   When (1) a list entry  1208  is located by keyed position, (2) entry creation or movement is requested, and (3) all entries on the list  1106  have a key of the specified entry locator key type greater than the specified key, the designated target position is the leftmost position in the list  1106 . 
   When (1) a list entry  1208  is located by keyed position, (2) entry creation or movement is requested, (3) at least one list entry  1208  on the list  1106  has a key of the specified entry locator key type less than the specified key, and (4) there is no list entry  1208  in the list  1106  that matches the specified key, then the designated target position is the first position after the rightmost entry with a key less than the specified list entry key in the list  1106 . 
   When a list entry  1208  is located by keyed position and entry creation or movement is requested, the designated target position exists when the list  1106  exists. 
   Comparing List Numbers 
   When the list number comparison type is active and a list entry  1208  is not created, a list number comparison is requested. 
   When list number comparison is requested, the list number object is compared with the list number specified. If they do not match, the list number comparison fails, command execution is completed with an appropriate response code or command execution continues by skipping the current list entry  1208 , depending on the command. 
   Comparing Counts 
   There are four sets of counts that are compared, depending on the process requested: the list set entry counts, the list set element counts, the event monitor controls counts, and the list entry counts or list element counts, depending on the element count indicator. 
   Comparing Event Monitor Controls Counts 
   The maximum event monitor controls count object is compared with the event monitor controls count object whenever an event monitor is registered and event monitor controls creation is requested. The event monitor controls object space is full when the maximum event monitor controls object equals the event monitor controls object. 
   Comparing List Element Counts 
   The list element count limit object is compared with the list element count object whenever a list entry  1208  is written or moved, the suppress list limit comparison control is inactive, and the element count indicator in the list structure type is active. If the sum of the list element count and the number of additional list elements  1214  required exceeds the list element count limit, the list  1106  is full. When the list  1106  is full and a write or move operation is requested, an appropriate response code is returned. 
   The list element count limit or list entry count limit is updated on a write list controls command, depending on the list control type. 
   Comparing List Entry Counts 
   The list entry count limit object is compared with the list entry count object whenever a list entry  1208  is created or moved, the suppress list limit comparison control is inactive, and the element count indicator in the list structure type is inactive. A list  1106  is full when the number of list entries  1208  created matches or exceeds the list entry count limit. When the list  1106  is full and a create or move operation is requested, an appropriate response code, depending on the command, is returned. 
   The record global lock manager command is an exception to list entry count limit comparison. 
   Comparing List Set Element Counts 
   The maximum list set element count object is compared with the list set element count object whenever a data list entry  1212  is written. If the sum of the list set element count and the number of additional list elements  1214  required exceeds the maximum list set element count, the list set  1104  is full. When the list set  1104  is full, and list entry creation or replacement, or retry data block creation is requested, an appropriate response code is returned. 
   Comparing List Set Entry Counts 
   The maximum list set entry count object is compared with the list set entry count object whenever a list entry  1208  is created. A list set  1104  is full when the number of list entries  1208  created and not deleted matches the maximum list set entry count. When a list set  1104  is full and list entry creation is requested, an appropriate response code, depending on the command, is returned. 
   Updating Counts 
   There are three types of counts that are updated, depending on the process requested: the list set entry count, the list set element count, and the list entry count or list element count, depending on the count indicator. 
   Updating the List Element Counts 
   The list element counts are updated when the element count indicator in the list structure type is active and a list entry  1208  is created, deleted, moved to another list  1106 , or replaced and the number of list elements  1214  associated with the list entry  1208  is changed or a retry data block is created or deleted. When the list entry  1208  is also the retry data block, the count is at most incremented or decremented by the number of list elements  1214  associated with the list entry  1208 . 
   Updating the List Entry Counts 
   The list entry counts are updated when the element count indicator in the list structure type is inactive and a list entry  1208  is created, deleted, or moved to another list  1106 . 
   Updating the List Set Element Count 
   The list set element count is updated whenever a list entry  1208  is created, deleted, or replaced and the number of list elements  1214  associated with the list entry  1208  is changed. 
   Updating the List Set Entry Count 
   The list set entry count is updated whenever a list entry  1208  created or deleted. 
   Comparing Version Numbers 
   Version numbers may be compared when an entry is replaced, read, moved, or deleted, or when an adjunct lock entry is updated by an adjunct locking operation, depending on the version request type and the version comparison request type specified. When the first bit of the version request type is B‘1’, the version number object is compared with the CVN request operand  1010 . When the VCRT is B‘0’ and they are equal or when the VCRT is B‘1’ and the version number object is less than or equal to the CVN operand, the comparison is successful and the command continues. If the comparison fails, command execution is completed with an appropriate response code or command execution continues by skipping the current list entry  1208 , depending on the command. 
   Updating a Version Number 
   When an entry is created, replaced, read, or moved, or when an adjunct lock entry is updated by an adjunct locking operation, a version number may be updated depending on the version request type specified. 
   When a version request type of B‘ 001 ’ is specified, or a version request type of B‘101’ is specified and version number comparison is successful, the version number is decremented by one. 
   When a version request type of B‘010’ is specified, or a version request type of B‘110’ is specified and version number comparison is successful, the version number is incremented by one. 
   When a version request type of B‘011’ is specified, or a version request type of B‘111’ is specified and version number comparison is successful, the version number object is set to the version number request operand  1010 . 
   Updating the List Assignment Key 
   The assignment key for the target list  1106  may be updated on a move list entry, a move list entries, a move and read list entry, a write and move list entry, or a write list entry command. 
   When the assignment key request type indicates that the key is assigned, the conditions for key assignment for the designated list entry  1208  are satisfied as specified by the AKRT operand, and the assignment key update type is increment the value of the assignment key increment is added to the assignment key and the resultant is compared with the assignment key threshold. If the resultant is less than or equal to the assignment key threshold, the resultant is stored in the assignment key. If the resultant is greater than the assignment key threshold, the assignment key is not updated and an appropriate response code is returned. 
   Writing a List Entry 
   A list entry  1208  may be written on a write list entry or a write and move list entry command. A list entry  1208  is written when an entry is created or replaced. 
   When a list entry  1208  is created, the data and adjunct indicators within the list structure type object are used to determine whether or not to write the data or adjunct list entry, or both. When a list entry  1208  is replaced, the data and adjunct indicators within the list entry type operand are used to determine whether or not to write the data or adjunct list entry, or both. 
   When the data indicator is active, the data list entry  1212  is written from the data block  1006 . When the adjunct indicator is active, the adjunct list entry  1216  is written from the adjunct list entry value request operand  1010 . 
   When the data list entry  1212  is replaced and the data list entry size operand is smaller than the data list entry size object, the data list entry is contracted to the new size, the data block  1006  is stored in the data list entry, and the data list entry size object in the list entry controls  1210  is updated with the value of the data list entry size operand. When the data list entry  1212  is replaced and the data list entry size operand is larger than the data list entry size object, the data list entry is expanded to the new size, the data block  1006  is stored in the data list entry, and the data list entry size object in the list entry controls  1210  is updated with the value of the data list entry size operand. 
   When an adjunct list entry  1216  is replaced and secondary keys are supported in the structure, bytes  0  to  31  in the adjunct list entry value request operand  1010  are not stored and bytes  32  to  63  in the adjunct list entry value request operand  1010  are stored in the secondary adjunct data entry. The secondary list entry key is not changed when the adjunct list entry  1216  is replaced. 
   Creating a List Entry 
   List entry creation is requested on a write list entry or write and move list entry command, depending on the write request type specified. List entry creation is also requested on a record global lock manager command or may be also requested by an adjunct lock request process. 
   When a write request type of create list entry is specified, list entry creation is unconditionally requested. When a write request type of replace or create list entry is specified, list entry creation is conditionally requested; that is, the list entry creation is requested when the designated list entry  1208  does not exist. 
   When the list set  1104  and the target list  1106  is not full and list entry creation is requested, a list entry  1208  may be created. When a list entry  1208  is created on the target list  1106 , (1) the list set entry count and when it exists, the associated list entry count are each incremented by one, (2) the list set element count and when it exists, the associated list element count are each increased by the value of the data list entry size, and (3) the write result response operand (WRES)  1014  is set to “a new list entry was created”. 
   A list entry  1208  is created at the first entry position relative to the designated target position, and the relative position of all succeeding entries is increased by one. 
   When a keyed entry is created by executing the write list entry command, if the AKRT operand is either assigned on create or assigned on create or move, and if the assignment key object in the target list  1106  is less than or equal to the assignment key threshold object, then the target key is set to the value of the assignment key object in the target list  1106  prior to updating the list assignment key. If the AKRT operand is either assigned on create or assigned on create or move, and if the assignment key object in the target list  1106  is greater than the assignment key threshold object, the command is completed without creating the list entry  1208 , and an appropriate response code is returned. 
   When a keyed entry is created by executing the write and move list entry command and if the AKRT operand is either not assigned or assigned on move, the MELT operand specifies which key value the target key is set to: zero means the LEK in MCB and one means the TLEK in MCB. If the AKRT operand is either assigned on create or assigned on create or move, and if the assignment key object in the target list  1106  is less than or equal to the assignment key threshold object, then the target key is set to the value of the assignment key object in the target list  1106  prior to updating the list assignment key. If the AKRT operand is either assigned on create or assigned on create or move, and if the assignment key object in the target list  1106  is greater than the assignment key threshold object, the command is completed without creating the list entry  1208 , and an appropriate response code is returned. 
   When a write request type of create list entry is specified and the list entry name already exists, an appropriate response code is returned. 
   When a list entry  1208  is created with a program list entry identifier indicator value of inactive, the coupling facility generates the list entry identifier value. 
   When a list entry  1208  is created with a program list entry identifier indicator value of active, the list entry identifier value for the entry is the value provided by the program in the list entry identifier operand in the MCB for the command. The LEID value stored in the list entry  1208  is the LEID operand. The LEID value is checked to ensure that it is unique in the structure. There is no requirement for the LEID value to be unique for any specific length of time and may be reused once the entry which has that LEID assigned to it is deleted. 
   Replacing a List Entry 
   A list entry  1208  may be replaced on a write list entry or write and move list entry command. 
   When a write request type of replace list entry or replace or create list entry is specified and the designated list entry  1208  exists, the list entry  1208  may be replaced. 
   When a list entry  1208  is replaced, the list set element count and when it exists, the associated list element count are each increased or decreased by the change in the data list entry size, and the write result response operand (WRES)  1014  is set to existing list entry replaced. 
   When a write request type of replace list entry is specified and the designated list entry  1208  does not exist, an appropriate response code is returned. 
   The position of an entry is not affected when it is replaced. 
   Reading a List Entry 
   A list entry  1208  may be read on a read list entry, move and read list entry, or read and delete list entry command, and one or more list entries  1208  may be read on a read list or read list set command. 
   When the data indicator in the list entry type specified is active, one or more data list entries  1212  may be read into the data area, depending on the command executed. When the adjunct indicator in the list entry type specified is active, one adjunct list entry  1216  may be read into the adjunct list entry value response operand  1014 , or one or more adjunct list entries are read into the data area, depending on the command executed. 
   When a read list or read list set command is executed, the adjunct or data list entries are always read into the data area. Otherwise, when any other command that does a read operation is executed, the adjunct list entry  1216  is read into the response operand  1014 . 
   The position of an entry is not affected by a read operation. 
   Moving a List Entry 
   A list entry  1208  may be moved on a move list entry, move list entries, write and move list entry, or a move and read list entry command. List entries  1208  may be moved between lists  1106  or to the same list  1106  within a list set  1104 . 
   The source list  1106  is the list  1106  associated with the designated list entry  1208 . The target list  1106  is the list  1106  associated with the designated target position. 
   When a list entry  1208  is moved from one list  1106  to another and the list entry count exists, the list entry count of the source list  1106  is decremented by one and the list entry count of the target list  1106  is incremented by one. 
   When a list entry  1208  is moved from one list  1106  to another and the list element count exists, the list element count of the source list  1106  is decreased by the value of the data list entry size and the list element count of the target list  1106  is increased by the same amount. 
   A list entry  1208  is moved from the first entry position relative to the designated position, and the relative position of all succeeding entries is decreased by one. 
   A list entry  1208  is moved to the first entry position relative to the designated target position, and the relative position of all succeeding entries is increased by one. 
   When a keyed entry is moved and if the AKRT operand is either not assigned or assigned on create, the MELT operand specifies which key value the target key is set to zero means the LEK in the list entry  1208  and one means the TLEK in MCB. 
   If the AKRT operand is either assigned on move or assigned on create or move, and if the assignment key object in the target list  1106  is less than or equal to the assignment key threshold object, then the target key is set to the value of the assignment key object in the target list  1106  prior to updating the list assignment key. 
   If the AKRT operand is either assigned on move or assigned on create or move, and if the assignment key object in the target list  1106  is greater than the assignment key threshold object, the command is completed without creating the list entry  1208 , and an appropriate response code  10  is returned. 
   A list entry key is updated by the move process if the target key is set to either the TLEK request operand  1014  or the assignment key object. The value of the list entry key may or may not be changed when it is updated. A list entry key is not updated by the move process if the target key is set equal to the list entry key object. 
   Similarly, a secondary list entry key is updated by the move process if the target secondary key is set to the value of the TSLEK request operand  1010 , and is not updated by the move process if the target secondary key is set equal to the SLEK object. The value of the secondary list entry key may or may not be changed when it is updated. 
   When a keyed entry is moved to the same list  1106 , the LEK object is not updated by the move process, and the MPKP operand is active, the TDIR operand is ignored and the designated primary key position is not changed. 
   When a keyed entry with secondary keys is moved to the same list  1106 , the SLEK object is not updated by the move process, and the MSKP operand is active, the STDIR operand is ignored and the designated secondary key position is not changed. 
   When a keyed entry with secondary keys is moved to the same list  1106 , neither the LEK nor the SLEK object are updated, and both the MPKP and MSKP operands are active, the TDIR and STDIR operands are ignored and no move operation occurs. 
   When a keyed entry with secondary keys is moved by a move list entries command, the SMELT operand specifies which key value the target secondary key is set to; inactive means the SLEK in the list entry  1208  and active means the TSLEK in the move block. When a list entry  1208  is moved by any other command, the SLEK is not changed. Assignment keys are not supported for secondary keys. 
   Deleting a List Entry 
   A list entry  1208  may be deleted on a delete list entry or read and delete list entry command and one or more list entries  1208  may be deleted on a delete list, delete list set or delete list entries command. 
   When a list entry  1208  is deleted, the list set entry count and when it exists, the list entry count are each decreased by one. 
   When a list entry  1208  is deleted, the list set element count and when it exists, the list element count are each decreased by the value of the data list entry size. 
   An entry is deleted at the first entry position relative to the designated position, and the relative position of all succeeding entries is decreased by one. 
   Notifying a Key Range Monitor 
   When a key range state transition occurs, one or more list notification commands are initiated for the key range. 
   When registration of a key range monitor is performed and the initial notification request type operand is active, one or more list notification commands are performed as primary processes for the user. When the specified key range is empty, a list notification command indicating a not-empty-to-empty key range state transition is performed; when the specified key range is not empty, a list notification command indicating an empty-to-not-empty key range state transition is performed. 
   Registration of a key range monitor may receive a list notification even if the initial notification request type operand is inactive and no key range state transition occurs. This is because the list notification command had been pending since before the last deregistration. 
   All commands capable of creating, deleting, or moving a list entry  1208  initiate list notification commands as secondary processes for the designated key range that changes state. 
   Updating the List Cursor 
   When the list cursor request type (LCURT) operand is active, the list cursor of the list  1106  in which the designated list entry  1208  resides is updated. When the list  1106  is keyed, the list order used in identifying the next and previous list entries  1208  is the primary key order. 
   When LCURT is inactive or not provided along with the command, no list cursor is updated with two exceptions. The two exceptions are: (1) when a list entry  1208  associated with a list cursor position is moved to another list  1106 , and (2) when a list entry  1208  associated with a list cursor position is deleted. In these two cases, the list cursor of the list  1106  in which the designated list entry  1208  resides is reset to zero. 
   When the LCURT operand is active, the list cursor is updated. The updated value of the list cursor depends on the designated position or target position, the specified direction, and the specified list cursor update type (LCUT) operand. 
   List cursor updated to next entry: When a list cursor update type of update cursor to next entry is specified, the list cursor is updated to the list entry identifier of the next list entry  1208  as specified by the designated list entry  1208  and the direction subject to the following boundary conditions:
     1. When the designated list entry  1208  is the leftmost entry on the list  11106  and a right-to-left direction is specified, the list cursor is reset to zero.   2. When the designated list entry  1208  is the rightmost entry on the list  1106  and a left-to-right direction is specified, the list cursor is reset to zero.   

   When a list entry  1208  is created by executing the write and move list entry command, the direction is specified by the TDIR operand; otherwise, the direction is specified by the DIR operand. 
   List cursor updated to current entry: When a list cursor update type of update cursor to current entry is specified, the list cursor is updated to the list entry identifier of the designated list entry  1208 , provided the designated list entry  1208  is not being deleted or moved to another list  1106 . When the designated list entry  1208  is being deleted or moved to another list  1106 , the list cursor is set to zero. 
   List cursor maintained at next entry: When a list cursor update type of maintain cursor at next entry is specified and the list entry  1208  associated with the list cursor position is deleted or moved, the list cursor is updated to the list entry identifier of the next list entry  1208  as specified by the designated list entry  1208  and the cursor direction list control subject to the following boundary conditions:
     1. When the designated list entry  1208  is the leftmost entry on the list  1106  and the cursor direction is right to left, the list cursor is reset to zero.   2. When the designated list entry  1208  is the rightmost entry on the list  1106  and the cursor direction is left to right, the list cursor is reset to zero.   

   When the list entry  1208  associated with the list cursor exists and is not being deleted or moved, the list cursor is not updated. 
   List cursor maintained at current entry: When a list cursor update type of maintain cursor at current entry is specified and the list cursor is zero, the list cursor is updated to the list entry identifier of the designated list entry  1208 , provided the designated list entry  1208  is not being deleted or moved to another list  1106 . When the designated list entry  1208  is being deleted or moved to another list  1106 , the list cursor remains zero. 
   When the list entry  1208  associated with the list cursor exists and is not being deleted or moved to another list  1106 , the list cursor is not updated. When the designated list entry  1208  is being deleted or moved to another list  1106 , the list cursor is reset to zero. 
   Registering a Monitor 
   A monitor is registered by means of the register list monitor or register event monitors command. A list structure user may register as a monitor when the user is attached with a nonzero list notification token. 
   The register list monitor command can be used to register any of the following four types of monitors: list, event queue, event monitors, and key range. The monitor request type operand is provided to specify the monitor type. The register event monitors command is used to register a number of event monitors. 
   When the monitor request type operand specifies a list monitor, the list monitoring active flag is set, and the list notification request type and list notification entry number are updated in the list monitor table entry  1304  of the specified list  1106  and user. 
   When the monitor request type operand specifies an event queue monitor, the event queue  1116  of the specified key type is initialized. The event queue monitoring active flag is set, and the event notification request type and event notification entry number are updated in the event queue controls. 
   When the monitor request type operand specifies an event monitor or a register event monitors command is executed, the event monitor controls object  1306  of the specified key type of each specified subsidiary list and user is created if it does not exist, and is updated if it does exist. 
   When the monitor request type operand specifies a key range monitor, the key range monitoring active flag is set, and the key range notification request type and the key range notification entry number are updated in the key range monitor table entry of the specified list  1106  and user. 
   Deregistering a Monitor 
   A monitor is deregistered by means of the deregister list monitor or detach list structure user command. The monitor request type operand is provided by the deregister list monitor command to specify the monitor type to be deregistered. 
   When a list monitor is deregistered, the list monitoring active flag is reset in the list monitor table entry  1304  of the specified list  1106  and user. 
   When an event queue monitor is deregistered, the event queue monitoring active flag, the event notification request type, and event notification entry number are reset for the event queue controls of the specified key type. 
   When an event monitor is deregistered the event monitor controls object  1306  associated with the user and the key type and the subsidiary list of the specified key type are deleted. 
   When a key range monitor is deregistered, the key range monitoring active flag is reset in the list monitor table entry  1304  of the specified list  1106  and user. 
   Handling of Event Monitor Controls 
   This section describes processes of creating, updating, queueing, dequeueing, deleting, and withdrawing an event monitor controls object  1306 . 
   Creating Event Monitor Controls: When a user registers interest in a subsidiary list by means of executing a register list monitor or register event monitors command, if the associated event monitor controls object  1306  does not exist, then an event monitor controls object  1306  is created for the user and the specified subsidiary list. 
   Updating Event Monitor Controls: When a user registers interest in a subsidiary list by means of executing a register list monitor or register event monitors command, if the associated event monitor controls object  1306  already exists, then the object is updated. 
   Queueing Event Monitor Controls: The event monitor controls queueing process may be a primary or secondary process, depending on its causing command. When an event monitor is registered by means of the register list monitor command, if the initial notification request type operand is active, the designated subsidiary list is not empty, and the designated event monitor controls object  1306  is not queued, then an event monitor controls queueing process is performed to queue the designated event monitor controls object  1306  to the event queue  1116  of the user as a primary process. When an event monitor is registered by means of the register event monitors command, if the initial notification request type operand is active, and the event monitor queue indicator control operand is inactive, the designated subsidiary list is not empty, and the designated event monitor controls object  1306  is not queued, then an event monitor controls queueing process is performed to queue the designated event monitor controls object  1306  to the event queue  1116  of the user as a primary process. When an event monitor is registered by means of the register event monitors command, if the initial notification request type operand is active, and the event monitor queue indicator control operand is active, the event monitor queue indicator operand is active, and the designated event monitor controls object  1306  is not queued, then an event monitor controls queueing process is performed to queue the designated event monitor controls object  1306  to the event queue  1116  of the user as a primary process. 
   When execution of a command causes an empty-to-not-empty or not-empty-to-not-empty subsidiary list state transition, an event monitor controls queueing process is initiated for the subsidiary list as a secondary process. All list structure commands capable of creating or moving a list entry  1208  may cause an empty-to-not-empty or not-empty-to-not-empty subsidiary list state transition. Execution of a pending event monitor controls queueing process queues every event monitor controls object  1306  that exists at that time and is associated with the designated subsidiary list to the event queue  1116  of the corresponding key type of the user specified in the event monitor controls object  1306 . No action is taken for those designated event monitor controls objects  1306  that are already queued. If no designated event monitor controls object  1306  exists, no action is taken and the process execution is complete. If there are two or more pending queueing and withdrawal processes for the same subsidiary list, only the most recently initiated process needs to be performed, and all previous queueing or withdrawal processes may be purged. Execution of an event monitor controls queueing process is complete before execution of a subsequent withdrawal process targeted to the same event monitor controls object  1306  begins. 
   Dequeueing Event Monitor Controls: The event monitor controls objects  1306  of a user are dequeued from the event queue  1116  by means of the dequeue event monitor controls command. 
   Deleting Event Monitor Controls: When a user deregisters an event monitor, the associated event monitor controls object  1306  is deleted and the event monitor controls deletion process performed is a primary process. 
   Withdrawing Event Monitor Controls: The event monitor controls withdrawal process may be a primary or secondary process, depending on its causing command. When an event monitor is registered by means of the register list monitor command, if the initial notification request type operand is active, the designated subsidiary list is empty, and the designated event monitor controls object  1306  is queued, then an event monitor controls withdrawal process is performed to withdraw the designated event monitor controls object  1306  from the event queue  1116  of the user as a primary process. When an event monitor is registered by means of the register event monitors command, if the initial notification request type operand is active, the event monitor queue indicator control operand is inactive, the designated subsidiary list is empty, and the designated event monitor controls object  1306  is queued, then an event monitor controls withdrawal process is performed to withdraw the designated event monitor controls object  1306  from the event queue  1116  of the user as a primary process. 
   When an event monitor is registered by means of the register event monitors command, if the initial notification request type operand is active, the event monitor queue indicator control operand is active, the event monitor queue indicator operand is inactive, and the designated event monitor controls object  1306  is queued, then an event monitor controls withdrawal process is performed to withdraw the designated event monitor controls object  1306  from the event queue  1116  of the user as a primary process. 
   When execution of a command causes a not-empty-to-empty subsidiary list state transition, an event monitor controls withdrawal process is initiated for the subsidiary list as a secondary process. All list structure commands capable of deleting or moving a list entry  1208  may cause a not-empty-to-empty subsidiary list state transition. 
   Execution of a pending event monitor controls withdrawal process removes every event monitor controls object  1306  that is associated with the designated subsidiary list from the event queue  1116  of the user specified in the event monitor controls object  1306 . No action is taken for those designated event monitor controls objects  1306  that are not queued. If no designated event monitor controls object  1306  is queued to any event queue  1116 , no action is taken and the process execution is complete. If there are two or more pending queueing and withdrawal processes for the same subsidiary list, only the most recently initiated process needs to be performed, and all previous queueing or withdrawal processes may be purged. Execution of an event monitor controls withdrawing process is complete before execution of a subsequent queueing process targeted to the same event monitor controls object  1306  begins. 
   Notifying an Event Queue Monitor 
   When an event queue state transition occurs, one or more list notification commands are generated for the event queue  1116 . 
   When registration of an event queue monitor is performed and the initial notification request type operand is active, one or more list notification commands are performed as primary processes for the user. When the specified event queue  1116  is empty, a list notification command indicating a not-empty-to-empty queue state transition is performed; when the specified event queue  1116  is not empty, a list notification command indicating an empty-to-not-empty queue state transition is performed. 
   Registration of an event queue monitor may receive an event queue notification even if the initial notification request type operand is inactive and no event queue state transition occurs. This is because the list notification command had been pending since before the last deregistration. 
   If performance of an event monitor controls queueing process or event monitor controls withdrawal process causes the designated event queue  1116  to change its state, and if the process is caused by executing a register list monitor or register event monitors command with the initial notification request type operand set to active, then one or more list notification commands are performed as primary processes. If the queueing or withdrawal process is caused by executing any other command, then one or more list notification commands are initiated as secondary processes. 
   If performance of an event monitor controls dequeueing process or event monitor controls deletion process causes the designated event queue  1116  to change its state, then one or more list notification commands are performed as primary processes. The only exception is that the event monitor controls deletion processes initiated by the detach list structure user command do not initiate any list notification command. 
   Notifying a List Monitor 
   When a list state transition occurs, one or more list notification commands are initiated for the list  1106 . 
   When registration of a list monitor is performed and the initial notification request type operand is active, one or more list notification commands are performed as primary processes for the user. When the specified list  1106  is empty, a list notification command indicating a not-empty-to-empty list state transition is performed; when the specified list  1106  is not empty, a list notification command indicating an empty-to-not-empty list state transition is performed. 
   Registration of a list monitor may receive a list notification even if the initial notification request type operand is inactive and no list state transition occurs. This is because the list notification command had been pending since before the last deregistration. 
   All commands capable of creating, deleting, or moving a list entry  1208  initiate list notification commands as secondary processes for the designated list  1106  that changes state. 
   Notifying a Key Range Monitor 
   When a key range state transition occurs, one or more list notification commands are initiated for the key range. When registration of a key range monitor is performed and the initial notification request type operand is active, one or more list notification commands are performed as primary processes for the user. When the specified key range is empty, a list notification command indicating a not-empty-to-empty key range state transition is performed; when the specified key range is not empty, a list notification command indicating an empty-to-not-empty key range state transition is performed. 
   Registration of a key range monitor may receive a list notification even if the initial notification request type operand is inactive and no key range state transition occurs. This is because the list notification command had been pending since before the last deregistration. 
   All commands capable of creating, deleting, or moving a list entry  1208  initiate list notification commands as secondary processes for the designated key range that changes state. 
   List Command Operands 
   Adjunct List Entry (ALE): A value that is read from or written to an adjunct list entry  1216 . This request operand  1010  is ignored unless the list structure  902  has adjunct list entries  1216  and (1) a create operation is requested, or (2) the list entry type specifies an adjunct list entry  1216  and a replace operation is requested. 
   Adjunct Format Control (AFC): A bit string consisting of adjunct format bits. Each bit is associated with a particular adjunct format. The adjunct format control bits include an adjunct secondary key indicator and adjunct lock entry indicator. 
   The bits are mutually exclusive; at most one bit is active. When all the bits are inactive, the adjunct is unformatted and contains the adjunct data list entry. 
   Allocation Type (AT): A four-bit value that indicates what action an allocate command should take. The first two bits are the ratio indicators (RI), the third bit is the structure size indicator (SSI), and the fourth bit is the user structure control indicator (USCI). 
   An allocation type of all inactive bits specifies that all list allocation processes are checkpointed and stopped. 
   The first bit of the ratio indicator is the monitor-to-entry storage ratio indicator (MTESRI), the second bit is the entry-to-element ratio indicator (ETELRI). 
   The monitor-to-entry storage ratio indicator is not meaningful at this granularity when inactive, but indicates when active to initiate or continue monitor-to-entry storage reapportionment as specified by the target monitor-to-entry storage ratio request operand, and, if ETELRI is inactive, resume entry-to-element reapportionment as specified by the pending entry-to-element ratio. 
   The entry-to-element ratio indicator is not meaningful at this granularity when inactive, but indicates when active to initiate or continue entry-to-element reapportionment as specified by the target entry-to-element ratio request operand, and, if MTESRI is inactive, resume monitor-to-entry storage reapportionment as specified by the pending monitor-to-entry storage ratio. 
   The structure size indicator in not meaningful at this granularity when inactive, but indicates when active to initiate or continue expansion or contraction as specified by the target structure size request operand, and resume each suspended reapportionment as specified by the associated pending ratio if the associated ratio indicator is zero. 
   The user structure control indicator indicates whether the user structure control is updated. 
   The structure authority is always compared and conditionally replaced. The allocation type is ignored unless the initial allocation process is complete. When the data indicator (DI) in the list structure type (LST) object is inactive, the entry-to-element ratio indicator (ETELRI) must be inactive; when the key indicator (KI) in the LST object is inactive, the monitor-to-entry storage ratio indicator (MTESRI) must be inactive. 
   Apportionment Priority Indicator (API): A flag directs the resolution of conflicts in the establishment of an accurate ratio in an expansion or contraction process or when the list  1106  is initially allocated. When active, it indicates that maintaining an accurate ratio is of higher priority than maximizing the amount of storage resources that are assigned to the structure. When inactive, it indicates that maximizing storage resources is of higher priority and a less accurate ratio will be tolerated. 
   This operand is ignored when a reapportionment process is specified and an expansion or contraction process is not specified, or when a list  1106  is initially allocated and the target counts priority indicator is active. 
   Assignment Key Increment (AKI): A four-byte unsigned binary integer that is added to the value of the assignment key when the assignment key is updated. This request operand  1010  is ignored unless the list entries  1208  are keyed, the assignment key request type indicates that the key is assigned, and the assignment key update type is increment. 
   Assignment Key Request Type (AKRT): A two-bit value that indicates when the list entry key is set to the value of the assignment key in the list controls  1202 . It may indicate that the list entry key is (1) not assigned, (2) assigned on move, (3) assigned on create, or (4) assigned on create or move. 
   Assignment Key Update Type (AKUT): A one-bit value that indicates how the assignment key is updated. It may indicate that the assignment key is (1) not updated or (2) incremented. 
   Comparative Global Lock Manager (CGLM): A value that is compared to the global lock manager object. This request operand  1010  is ignored unless the lock request type is valid and specifies a comparison of the global lock managers. 
   Comparative List Authority (CLAU): A value that is compared to the list authority object. 
   Comparative Structure Authority (CSAU): A value that is compared to the structure authority object. 
   Current Data Index (CDX): A value that indexes to the current list entry name or list entry identifier in the data block  1006  for the delete list entries command. 
   Current Event Index (CTX): A value that indexes to the current event in the data block  1006  for the register event monitors command. 
   Cursor Direction (CDIR): Indicates how the list cursor is updated (left to right or right to left) when the list cursor is maintained or initialized by a write list controls command. 
   Cursor Direction Type (CDT): Determines how the cursor direction and location is set for the write list controls command. When the cursor direction type bit is inactive, the list cursor is initialized to the leftmost or rightmost list entry  1208  based on the CDIR operand. When the cursor direction type bit is active, the list cursor is initialized based on the LEID and the CDIR operand. This operand is ignored if the list cursor bit in the LCT operand is inactive. 
   Data Block Size (DBS): Specifies the size of the data block  1006  as an integral multiple of 4096-byte units. Valid values range from 1 to 16 if the command is not read list structure controls. If the command is read list structure controls, valid values range from 0 to 16. 
   Data Entries Locator Type (DAELT): Indicates how a list entry  1208  is located for the move list entries command. 
   When the list structure  902  does not have list entry names, the operand may indicate locate by list entry identifier. 
   When the list structure  902  has list entry names, the operand may indicate (1) locate by list entry identifier or (2) locate by list entry name. 
   Data List Entry (DLE): A value that is read from or written to a data list entry  1212 . 
   Data List Entry Size (DLES): Specifies the size of the data list entry  1212  as an integral multiple of the list element size. 
   Delete Entries Locator Type (DELT): Indicates how a list entry  1208  is located for the delete list entries command. 
   When the list structure  902  does not have list entry names, the operand may indicate locate by list entry identifier. 
   When the list structure  902  has list entry names, the operand may indicate (1) locate by list entry identifier or (2) locate by list entry name. 
   Delete List Entries Count (DLEC): Specifies the number of deleted list entries  1208 . 
   Direction (DIR): indicates whether the positions of the list entries  1208  are numbered left to right or right to left relative to a designated position. 
   Element Toleration Factor (ELTF): When divided by 100, specifies the minimum number of data list elements  1214  that may still be assigned to list entries  1208  or retry data blocks, or both, after any checkpoint of a contraction, expansion, entry-to-element reapportionment, or monitor-to-entry storage reapportionment process as a percentage of the total number of existing data list elements  1214 . 
   Ending Data Index (EDX): Indexes to the last list entry name or list entry identifier in the data block  1006  for the delete list entries command. 
   Ending Event Index (ETX): Indexes to the last event in the data block  1006  for the register event monitors command. 
   Entry Locator Key Type (ELKT): Indicates the type of key (primary or secondary) that is used for locating a list entry  1208  when the entry locator type specifies locate by keyed position. 
   Event monitor queue indicator control (EMQIC): Controls EMC enqueueing or withdrawal. The EMQIC bit is ignored if the INRT bit is inactive. If the EMQIC bit is active and the INRT bit is active, the EMC is queued, not queued, withdrawn, or not withdrawn based on the EMQI bit. If the EMQIC bit is inactive and the INRT bit is active, the EMC is queued, not queued, withdrawn, or not withdrawn based on the state of the sublist. 
   Entry Locator Type (ELT): Indicates how a list entry  1208  is located for a read, replace, or delete operation, or as the source of a move operation. 
   When the list structure  902  does not have list entry names or list entry keys, the operand may indicate (1) locate by unkeyed position, (2) locate by list entry identifier, (3) locate by list cursor position. 
   When the list structure  902  has list entry names, the operand may indicate (1) locate by unkeyed position, (2) locate by list entry identifier, (3) locate by list entry name, or (4) locate by list cursor position. 
   When the list structure  902  has list entry keys, the operand may indicate (1) locate by unkeyed position, (2) locate by keyed position, (3) locate by list entry identifier, or (4) locate by list cursor position. 
   When a list entry  1208  is created, the entry locator type operand is ignored. Instead, for a create or move operation, the target list entry position is located by keyed position when the entries are keyed, or by unkeyed position when the entries are not keyed. 
   When a list set  1104  is not allocated, all ELTs are invalid. 
   Entry Toleration Factor (ETF): When divided by 100, specifies the minimum number of list entries  1208  that may still be created after any checkpoint of a contraction, expansion, entry-to-element reapportionment, or monitor-to-entry storage reapportionment process as a percentage of the total number of existing list entries  1208 . 
   Event Monitor Controls Dequeued Count (EMCDC): Specifies the number of event monitor controls objects  1306  dequeued by means of the dequeue event monitor controls command. 
   Event Monitor Toleration Factor (EMTF): When divided by 100, specifies the minimum number of event monitor controls  1306  that may still be created after any checkpoint of a contraction, expansion, entry-to-element reapportionment, or monitor-to-entry storage reapportionment process as a percentage of the total number of existing event monitor controls  1306 . 
   Event Notification Entry Number (ENEN): Specifies a list notification vector entry. 
   Event Notification Request Type (ENRT): Indicates whether the list notification vector summaries are to be updated when an empty to not-empty state transition occurs on a monitored event queue  1116 . 
   Event Queue Monitoring Active Bit (EQMAB): Specifies whether the user associated with the event queue  1116  is monitoring the event queue  1116 . 
   Failed Replacement Indicator (FRPI): When active, indicates that a replacement of the data list entry failed with a list set full condition and the size of the DLES operand is smaller than or equal to the size of the DLES object. 
   Granular Version Number Comparison (GVNC): indicates how the version number comparison is to be performed for move list entries and delete list entries commands. If the flag is active, the VCRT, VRT, CVN, and if applicable the VN in the data block  1006  are used to compare, and if applicable, replace, the version for the list entry  1208 , with each list entry  1208  in the data block  1006  having its own set of values. If the flag is inactive, the VCRT, VRT, CVN, in the MCB are used to compare the version for all list entries  1208  processed. 
   Halt on miscompare (HOM): Determines if the move list entries or delete list entries command stops processing on a miscompare. If the flag is active, processing of the command stops when a miscompare occurs. If the flag is inactive, processing of the command continues when a miscompare occurs. 
   Halt register event monitors (HREMS): Controls if an EMC is not registered and skipped or the registration process is halted. When the AOC bit is active and the HREMS bit is inactive, the EMC is skipped and processing continues if an EMC specifies a UID that is not assigned. When the AOC bit is active and the HREMS bit is active, processing is halted when an EMC that specifies a UID that is not assigned is processed. When the AOC bit is inactive and the HREMS bit is inactive, the EMC is skipped and processing continues if an EMC specifies a UID that is not attached. When the AOC bit is inactive and the HREMS bit is active, processing is halted when an EMC that specifies a UID that is not attached is processed. 
   Initial Notification Request Type (INRT): Indicates whether to notify a monitor of the initial state of the monitored object, except that when the request monitor type specifies an event monitor and the EMQIC bit is active, the initial state of the monitored object is ignored and the EMQI bit in the REMS registration block is used. 
   When the monitor request type specifies a list monitor, the initial notification request type indicates whether the list monitor is notified. 
   When the monitor request type specifies an event queue monitor, the initial notification request type indicates whether the event queue monitor is notified. 
   When the monitor request type specifies an event monitor, the initial notification request type indicates whether the event monitor controls object is queued or withdrawn, or no action taken. 
   When the monitor request type specifies a key range, the initial notification request type indicates whether the key range monitor is notified. 
   Key Comparison Type (KCT): Indicates whether key comparison is requested. 
   Key Range Empty Notification Threshold (KRENT): Specifies a number which is one less than the number of list entries  1208  that must remain in the key range to suppress a not-empty-to-empty list notification. 
   Key Range List Entry Key (KRLEK): Specifies the lower value of the key range. 
   Key Range Maximum List Entry Key (KRMLEK): Specifies the upper value of the key range. 
   Key Range Monitoring Active Bit (KRMAB): Specifies whether the user associated with the key range monitor table entry  1302  is monitoring the key range. 
   Key Range Not-empty Notification Threshold (KRNENT): Specifies one less than the number of list entries  1208  required in the key range in order to generate an empty-to-not-empty list notification. 
   Key Range Notification Entry Number (KRNEN): Specifies a list notification vector entry. 
   Key Range Notification Request Type (KRNRT): Indicates whether the list notification vector summaries are to be updated when an empty to not-empty state transition occurs on a monitored key range for the specified user identifier. 
   Key Request Type (KRT): Indicates how a keyed list entry  1208  is located when an entry is replaced, moved, read or deleted. For the read list command, when the key comparison type operand is active, the key request type operand also specifies how keys are compared. A two-bit value that indicates how a list entry  1208  is located when the entry locator type indicates location by keyed position, the entry locator key type is primary, and an entry is replaced, moved, read or deleted. When the key comparison type operand is active, the key request type operand also specifies how keys are compared. 
   The KRT operand is a dual purpose operand. When KCT is active, the KRT operand is used to control the type of list entry key comparison to be performed on a command. When the KCT is inactive, no list entry key comparison is performed. When ELT designates that an entry is located by keyed position, and the ELKT operand is primary, the KRT operand is used to control the type of entry location performed. When the ELT designates an entry location by a means other than keyed position, or the ELKT operand is secondary, the KRT has no effect on entry location. The type determines the relationship between the list entry key object and the list entry key and maximum list entry key operands. It may indicate a comparison for (1) equal to the list entry key operand, (2) less than or equal to the list entry key operand, (3) greater than or equal to the list entry key operand, or (4) within the range of the list entry key to the maximum list entry key operands, inclusive. 
   For the delete list entry, move and read list entry, move list entry, read and delete list entry, read list entry, write and move list entry, and write list entry commands the value “within the range” is invalid. For the delete list entries, delete list set, read list set, read list, delete list, and move list entries commands the value “within the range” specifies that the keyed list entry satisfies the search criterion or the key comparison criteria if it is within the range of the list entry key to the maximum list entry key operands, inclusive. 
   The key request type operand is ignored unless an entry is replaced, moved, read or deleted, and (1) the key comparison type is active, or (2) the entry locator type is locate by keyed position and the entry locator key type is primary. 
   Key Type (KT): Indicates the type of key (primary or secondary) that is used for selecting an event queue  1116  or the event monitor controls  1306  for a subsidiary list. 
   List Authority (LAU): A value that is conditionally updated. 
   List Authority Comparison Type (LAUCT): Indicates the procedure for comparing the list authority. It may indicate (1) do not compare list authorities, (2) compare list authority object and CLAU operand for being equal, or (3) compare list authority object for being less than or equal to the CLAU operand. 
   List Authority Replacement Type (LAURT): Indicates the procedure for updating the list authority. It may indicate (1) do not replace the list authority or (2) replace the list authority object with the LAU operand. 
   List Control Type (LCT): A bit string consisting of 16 consecutive list control update bits. Each bit is associated with a particular list control  1202 , and when active, causes the list control  1202  to be updated to a specified value. When the bit is inactive, the associated list control  1202  is not updated. The association of list control update bits to list controls  1202  is as follows: 
   
     
       
             
             
           
         
             
                 
             
             
               Bit 
               List control 
             
             
                 
             
           
           
             
               0-3 
               Invalid. 
             
             
                4 
               List state transition count 
             
             
                5 
               List empty notification threshold and List not-empty notification 
             
             
                 
               threshold 
             
             
                6 
               Key range empty notification threshold and Key range not-empty 
             
             
                 
               notification threshold 
             
             
                7 
               Key range maximum list entry key and Key range list entry key 
             
             
               8-10 
               Invalid 
             
             
               11 
               Assignment key. 
             
             
               12 
               Assignment key threshold. 
             
             
               13 
               List cursor and cursor direction. 
             
             
               14 
               User list control. 
             
             
               15 
               List element count limit or list entry count limit. 
             
             
                 
             
           
        
       
     
   
   Bits 6, 7, 11 and 12 are ignored unless the list entries  1208  are keyed. 
   List Count (LC): Specifies the number of lists  1106  to be allocated. 
   List Cursor Request Type (LCURT): Indicates whether the list cursor is to be updated. 
   List Cursor Update Type (LCUT): Indicates how a list cursor is updated when list cursor update is requested. It may indicate (1) update cursor to next entry, (2) update cursor to current entry, (3) maintain cursor at next entry, or (4) maintain cursor at current entry. 
   List Element Characteristic (LELX): Specifies the number of bytes in each list element  1214 . 
   List Element Count Limit (LELCL): Specifies the maximum number of list elements  1214  in a list  1106 . 
   List Empty Notification Threshold (LENT): Specifies a number which is one less than the number of list entries  1208  that must remain on the list  1106  to suppress a not-empty-to-empty list notification. 
   List Not-empty Notification Threshold (LNENT): Specifies one less than the number of list entries  1208  required on the list  1106  in order to generate an empty-to-not-empty list notification. 
   List Entry Count Limit (LECL): Specifies the maximum number of list entries  1208  in a list  1106 . 
   List Entry Identifier (LEID): An integer that designates the list entry  1208 . The LEID is written into the LEID object when the entry is created and into the list cursor object when a write list controls command updates the list cursor and the cursor direction type is active. 
   For LEIDs when the program list entry identifier indicator is inactive and a list entry  1208  is being created, a nonzero list entry identifier that is unique to a list set  1104  for at least 100 years is assigned by the coupling facility. 
   For LEIDs when the program list entry identifier indicator is active and a list entry  1208  is being created, the LEID value in the MCB is written into the LEID object for the list entry  1208 . The LEID value is checked to ensure that it is unique in the structure. There is no requirement for the LEID value to be unique for any specific length of time and may be reused once the entry which has that LEID assigned to it is deleted. 
   For LEIDs when the program list entry identifier indicator is active and a list entry  1208  is being created, the LEID value may be any value except zero, which is invalid. 
   When the command is write list controls, the LEID operand may be zero or must designate a list entry  1208  that exists on the list  1106  specified by the LN operand. The LEID operand is ignored on write list controls unless the list cursor bit and the cursor direction type are both active. 
   List Entry Key (LEK): Partially specifies a list entry position or an event monitor controls object  1306 . 
   List Entry Name (LEN): Fully specifies a list entry position. 
   List Entry Type (LET): Indicates which list entries  1208  are read or replaced upon normal completion of the command execution. The first bit is a data indicator (DI) that indicates whether or not a data list entry is read or written, and the second is an adjunct indicator (AI) that indicates whether or not an adjunct list entry is read or written. 
   List Monitoring Active Bit (LMAB): Specifies whether the user associated with the list monitor table entry  1304  is monitoring the list  1106 . 
   List Notification Entry Number (LNEN): Specifies a list notification vector entry. 
   List Notification Request Type (LNRT): Indicates whether the list notification vector summaries are to be updated when an empty to not-empty state transition occurs on a monitored list  1106 . 
   List Notification Token (LNT): Specifies a list notification vector to the system. 
   List Number (LN): An integer that designates a list  1106  in a list set  1104 . 
   List Number Comparison Type (LNCT): Indicates whether list number comparison is requested. 
   List Scan Key Type (LSKT): Indicates the key order (primary or secondary) used by a list scan process in a delete list or read list command. 
   Lock Request Type (LRT): A value that indicates the type of lock request. When a single list entry command is issued, the lock request type may be: (1) no lock process requested; (2) compare the global lock managers; (3) replace the global lock manager; (4) replace a local lock manager; or (5) replace the global lock and local lock managers. 
   When a multiple list entry command is issued, the lock request type may be: (1) no lock manager comparison; (2) compare the local lock managers; (3) compare the global lock or local lock managers; or (4) compare the global lock managers. 
   Lock Table Entry (LTE): A value that is read from a lock table entry  1112 . 
   Lock Table Entry Characteristic (LTEX): Specifies the number of bytes in each lock table entry  1112 . 
   Lock Table Entry Count (LTEC): Specifies the number of lock table entries  1112  to be allocated. 
   Lock Table Entry Number (LTEN): Specifies an entry in a lock table. 
   Maintain Primary Key Position (MPKP): Indicates whether the list entry  1208  is moved from its current position on a primary subsidiary list when the target list number specifies the list  1106  that contains the list entry  1208 , and the list entry  1208  key is not changed by the move operation. 
   Maintain Secondary Key Position (MSKP): Indicates whether the list entry  1208  is moved from its current position on a secondary subsidiary list when the target list number specifies the list  1106  that contains the list entry  1208 , and the secondary list entry key is not changed by the move operation. 
   Maximum Data List Entry Size (MDLES): Specifies the maximum size of the data list entry  1212  as an integral multiple of the list element size. 
   Maximum List Entry Key (MLEK): Partially specifies the maximum value the list entry key can have when the key compare type indicates key comparison and the key request type compares the key within range, or entry location by key range is specified and the ELKT operand is primary. 
   Maximum Secondary List Entry Key (MSLEK): Partially specifies the maximum value the secondary list entry key can have when the secondary key comparison type indicates key comparison, the secondary key request type compares the key within range, or entry location by key range is specified and the entry locator key type is secondary. 
   Maximum Structure Size (MXSS): Specifies the maximum number of 4,096-byte units allocated. 
   Minimum Required Control Storage (MRCS): Specifies the minimum number of 4K-byte units that must be allocated from control storage. 
   Monitor Request Type (MRT): Indicates what type of monitor to register or deregister. It may indicate (1) a list monitor, (2) an event queue monitor, (3) an event monitor, or (4) a key range monitor. 
   Monitored Object State (MOS): Indicates the state of the monitored object: empty (0) or not empty (1). 
   Monitored Object State Vector (MOSV): A bit string where the bit positions start at 0 and increase sequentially to 1K−1. The bit at position (i) in the string is set to one when the corresponding event monitor as specified in the data block  1006  of the register event monitors command is registered as a result of the command execution and the corresponding subsidiary list is not empty (i equals the event index minus one). Bit positions CTX−1 to ETX−1, and, when STX is greater than one, bit positions 0 to STX−2 are zero regardless of the state of the corresponding subsidiary list. Bit positions ETX to 1K−1 are reserved. 
   Move Entry Locator Type (MELT): A value that specifies which key value the target key is set to when (1) a list entry is created or moved by executing a move list entry, move and read list entry, move list entries, or write and move list entry command and (2) the AKRT operand indicates that the key is not assigned or the conditions of setting the target key to the assignment key as specified by the AKRT operand with a nonzero value are not satisfied. 
   For a list entry creation process, the operand indicates (when inactive) set to the list entry key in the MCB or (when active) set to the target list entry key in the MCB. 
   For a list entry movement process, the operand indicates (when inactive) set to the list entry key in the list entry or (when active) set to the target list entry key in the MCB. 
   This request operand  1010  is ignored when the list entries  1208  are not keyed and the command is not MLES or when AKRT takes precedence over MELT in one of the following conditions:
     1. A list entry creation process is performed and the AKRT operand is assigned on create or assigned on create or move, or   2. A list entry movement process is performed and the AKRT operand is assigned on move or assigned or create or move.   

   The operand must be zero if (1) the command is MLES, (2) the list entries  1208  are not keyed, and (3) AKRT does not take precedence. 
   For the move list entry, move and read list entry, move list entries, and write and move list entry commands, both MELT and AKRT are provided as input operands. However, AKRT takes precedence over MELT, and MELT takes effect only if AKRT indicates that the key is not assigned or the conditions specified by an AKRT that indicates that the key is assigned are not satisfied. 
   For a list entry creation process, the following table summarizes the target key assignment scenarios. 
   
     
       
             
           
             
             
             
           
             
             
             
             
           
         
             
                 
             
             
               Target Key Assignment for Creating a List Entry 
             
           
        
         
             
                 
               Write and Move List Entry 
                 
             
           
        
         
             
               AKRT 
               MELT = LEK 
               MELT = TLEK 
               Write List Entry 
             
             
                 
             
             
               Not assigned 
               LEK in MCB 
               TLEK in MCB 
               LEK in MCB 
             
             
               Assigned on 
               LEK in MCB 
               TLEK in MCB 
               LEK in MCB 
             
             
               move 
             
             
               Assigned on 
               Assignment Key 
               Assignment Key 
               Assignment Key 
             
             
               create 
             
             
               Ass&#39;d on 
               Assignment Key 
               Assignment Key 
               Assignment Key 
             
             
               create/move 
             
             
                 
             
           
        
       
     
   
   For a list entry move process, the following table summarizes the target key assignment scenarios. 
   
     
       
             
           
             
             
           
             
             
             
           
             
           
             
             
           
             
             
             
           
         
             
                 
             
           
           
             
               Target Key Assignment for Moving a List Entry 
             
           
        
         
             
                 
               Move List Entry, Move and Read List 
             
             
                 
               Entry, Write and Move List Entry 
             
           
        
         
             
               AKRT 
               MELT = LEK 
               MELT = TLEK 
             
             
                 
             
             
               Not assigned 
               LEK in the list entry 
               TLEK in MCB 
             
             
               Assigned on move 
               Assignment Key 
               Assignment Key 
             
             
               Assigned on create 
               LEK in the list entry 
               TLEK in MCB 
             
             
               Assigned on create or move 
               Assignment Key 
               Assignment Key 
             
             
                 
             
           
        
         
             
               Target Key Assignment for Moving List Entries 
             
           
        
         
             
                 
               Move List Entries 
             
           
        
         
             
               AKRT 
               MELT = LEK 
               MELT = TLEK 
             
             
                 
             
             
               Not assigned 
               LEK in the list entry 
               TLEK in the Data 
             
             
                 
                 
               Block 
             
             
               Assigned on move 
               Assignment Key 
               Assignment Key 
             
             
               Assigned on create 
               LEK in the list entry 
               TLEK in the Data 
             
             
                 
                 
               Block 
             
             
               Assigned on create or move 
               Assignment Key 
               Assignment Key 
             
             
                 
             
           
        
       
     
   
   Move List Entries Count (MLEC): Specifies the number of moved list entries  1208 . 
   Read List Entries Count (RLEC): Specifies the number of list entries  1208  read. 
   Read List Type (RLT): Indicates what values are read upon normal completion of the command execution. The first bit is a control indicator (CI) that indicates whether list entry controls are read, the second is a data indicator (DI) that indicates whether data list entries are read, and the third is an adjunct indicator (AI) that indicates whether adjunct list entries are read. 
   Restart Token (RT): Controls the reading or deleting of list entries on the read list set and delete list set commands. 
   Retry Index (RX): Designates a retry buffer. 
   Retry Version Number (RVN): Specifies the version number stored in the retry buffer. 
   Secondary Key Comparison Type (SKCT): Indicates whether secondary key comparison is requested. 
   Secondary Key Request Type (SKRT): A value that indicates how a list entry  1208  is located when the entry locator type indicates location by keyed position, the entry locator key type is secondary and an entry is replaced, moved, read or deleted. When the secondary key comparison type operand is active, the secondary key request type operand also specifies how secondary keys are compared. 
   The SKRT operand is a dual purpose operand. When SKCT is active, the SKRT operand is used to control the type of secondary list entry key comparison to be performed on a command. When the SKCT is inactive, no secondary list entry key comparison is performed. When ELT designates that an entry is located by keyed position, and the ELKT operand is secondary, the SKRT operand is used to control the type of entry location performed. When the ELT designates an entry location by a means other than keyed position, or the ELKT operand is primary, the SKRT has no effect on entry location. 
   The secondary key request type determines the relationship between the secondary list entry key object and the secondary list entry key operand. It may indicate a comparison for (1) equal to the secondary list entry key operand, (2) less than or equal to the secondary list entry key operand, (3) greater than or equal to the secondary list entry key operand, or (4) within the range of the secondary list entry key to the maximum secondary list entry key operands, inclusive. 
   For the delete list entry, move and read list entry, move list entry, read and delete list entry, read list entry, write and move list entry, and write list entry commands the value “within the range” is invalid. For the delete list entries, delete list set, read list set, read list, delete list, and move list entries commands the value “within the range” specifies that the secondary keyed list entry satisfies the search criterion or the secondary key comparison criterion if it is within the range of the secondary list entry key to the maximum secondary list entry key operands, inclusive. 
   The secondary key request type operand is ignored unless an entry is replaced, moved, read or deleted, and (1) the secondary key comparison type is active, or (2) the entry locator type is locate by keyed position and the entry locator key type is secondary. 
   Secondary List Entry Key (SLEK): Partially specifies a list entry position by secondary key or an event monitor controls object  1306 . 
   Secondary Move Entry Locator Type (SMELT): Specifies which key value the target secondary key is set to when a move list entries command is executed. When inactive it indicates do not change the SLEK; when active it indicates set to TSLEK in the move block. 
   Secondary Target Direction (STDIR): Indicates how the positions of the list entries  1208  are numbered relative to a designated target position in secondary key order for an entry moved by a move and read list entry, move list entries, move list entry, or write and move list entry command, or created by a write and move list entry or write list entry command. 
   Starting Data Index (SDX): Indexes to the first list entry name or list entry identifier in the data block  1006  for the delete list entries command. 
   Starting Event Index (STX): Indexes to the first event in the data block  1006  for the register event monitors command. 
   Structure Authority (SAU): A value that is conditionally updated. 
   Suppress List Count Comparison Control (SLCCC): When active, suppresses the comparison of the list entry count and the list element count with the list entry and list element count limit when a list entry  1208  is written or moved. 
   Target Direction (TDIR): Indicates how the positions of the list entries  1208  are numbered relative to a designated target position for a moved list entry  1208 . 
   Target List Entry Key (TLEK): Partially specifies the targeted position, in primary key order, to which a list entry  1208  is moved. 
   Target List Number (TLN): Designates the list  1106  to which a list entry is moved. 
   Target Secondary List Entry Key (TSLEK): Partially specifies the targeted position, in secondary key order, to which a list entry  1208  is moved by a move list entries command. 
   User Identifier (UID): An integer that identifies a user. When the lock request type specifies global lock manager and local lock managers replacement, the user identifier specifies a global lock manager. When the lock request type specifies global lock manager replacement, the user identifier specifies a global lock manager and, when local lock managers exist, it also specifies a local lock manager. When the lock request type specifies local lock manager replacement or local lock manager comparison, the user identifier specifies a local lock manager. 
   The UID must be assigned for a register event monitors command or register list monitor command when the attachment override control is active, the UID must be attached for a register event monitors command or register list monitor command when the attachment override control is zero, and must be attached for all other commands. 
   User List Control (ULC): A field per list  1106  defined by the user. 
   User Notification Control (UNC): A field per event monitor controls  1306  defined by the user. 
   User Structure Control (USC): A field per structure defined by the user. 
   Write event queue transition count (WEQTC): Controls if the EQTC object is written by the RLM command. When the WEQTC bit has a value of active and the monitor request type specifies register event queue monitor, the EQTC object is written. Otherwise, the EQTC object is not written. 
   Write Request Type (WRT): Indicates the type of write request. It may indicate (I) replace a list entry, (2) create a list entry, or (3) replace or create a list entry. 
   Write Result (WRES): A value that indicates whether a write completed by creating a new list entry  1208  or replacing an existing list entry  1208 . 
   List Commands 
   Delete List (DL) 
   Conditionally deletes all entries on a specified list  1106  that match the criteria of the version number comparison and/or key comparison requests starting from a designated position. Processing continues until the end of the list  1106  is reached or a designated time period has elapsed. 
   Description: When requested, the list authorities, the list numbers, global lock managers, local lock managers, or any combination, are compared before the first list entry  1208  is scanned. The list entries  1208  are scanned starting at the designated position and proceeding in the direction specified until a model dependent time period elapses or the last list entry  1208  is scanned. Each list entry  1208  is located and, when requested, the version numbers are compared, or the keys are compared, or any combination of the preceding processes is performed. In order for any list entries  1208  to be deleted, 1) the list authority comparison, 2) the list number comparison, and 3) the global lock manager or local lock manager comparison, when requested, must succeed. In order for a particular list entry  1208  to be deleted, the version number comparison and key comparison, when requested, must succeed. 
   When the list structure  902  supports secondary keys, the list order that is followed by the scan process is determined by the list scan key type operand. When the list scan key type is primary, the scan follows primary key order. When the list scan key type is secondary, the scan follows secondary key order. 
   When a list entry  1208  is deleted and a monitored list state transition results, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored subsidiary list state transition results, the associated event monitor controls objects  1306  are withdrawn. If this causes event queue transitions, the event queue monitors are notified. The withdrawal of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored key range state transition results, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When the last list entry  1208  is scanned, the delete list entries count equaling the number of list entries  1208  deleted during the final redrive of the DL command and an appropriate response code are returned in the response operands  1014 . 
   When a model dependent time period has elapsed, then the delete list entries count equaling the number of list entries  1208  deleted, the list entry controls  1210  of the next list entry  1208  in the sequence to be scanned, and an appropriate response code are returned in the response operands  1014 . 
   When the list authority comparison, the global lock manager comparison, or the local lock manager comparison fails during the processing of a list entry  1208  other than the designated list entry  1208 , then the delete list entries count equaling the number of list entries  1208  deleted, the list entry controls  1210  of the list entry  1208  that caused the mismatch and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested version number comparison fails, the located entry is not deleted and command execution continues to process the next list entry  1208 . 
   When the LRT operand indicates to compare the local lock managers and the local lock manager comparison fails during the processing of the designated list entry  1208 , the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock managers and the global lock manager comparison fails during the processing of the designated list entry  1208 , the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock or local lock managers, and both the global lock manager comparison and local lock manager comparison fail during the processing of the designated list entry  1208 , the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails during the processing of the designated list entry  1208 , the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the located entry is not deleted and command execution continues to process the next list entry  1208 . 
   Delete List Entries (DLES) 
   Conditionally deletes a set of list entries  1208  specified in an input list  11106  that match the criteria of the version number comparison and/or key comparison requests. Processing continues until the end of the input list  1106  is reached or a designated time period has elapsed. 
   Description: The list entries  1208  within the list set  1104  are processed starting with the list entry  1208  specified by the starting data index and continuing in the order as specified in the data block  1006 . 
   As part of processing each list entry  1208 , the list authority comparison, and the global lock manager comparison or the local lock manager comparison, if requested, are performed before the entry is located. If any of these comparisons fails, command execution concludes with an appropriate response code. If all of these comparisons are successful, command execution proceeds. 
   The entry is then located. To determine if the located entry is to be deleted, the version number comparison, the list number comparison, the key comparison, and the secondary key comparison, if requested, are performed. If any of these comparisons fails, then the located entry is not deleted and command execution continues to process the next list entry  1208 . In order for the located list entry  1208  to be deleted, all of these comparisons must succeed. 
   When the granular version number comparison flag is active, the VCRT, VRT, and CVN in the data block  1006  are used to do a version number comparison for each entry, the comparison values in the data block  1006  for the entry is used only for that list entry  1208 . When the granular version number comparison flag is inactive, the VCRT, VRT, and CVN in the MCB is tested for the list entries  1208  to be deleted, the comparison values in the MCB are used for all list entries  1208 . 
   When the halt on miscompare flag is active, the designated list entry  1208  exists but the requested version number comparison fails, then the processing stops, and the designated list entry controls and an appropriate response code are returned in the response operands  1014 . 
   When the halt on miscompare flag is active, the designated list entry  1208  exists but the requested list number comparison fails, then the processing stops, and the designated list entry controls and an appropriate response code are returned in the response operands  1014 . 
   When the halt on miscompare flag is active, the designated list entry  1208  exists but the requested key comparison fails, then the processing stops, and the designated list entry controls and an appropriate response code are returned in the response operands  1014 . 
   When a list entry  1208  is deleted and a monitored list state transition results, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored subsidiary list state transition results, the associated event monitor controls objects  1306  are withdrawn. If this causes event queue transitions, the event queue monitors are notified. The withdrawal of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored key range state transition results, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When the last list entry  1208  specified by the ending data index is processed, the delete list entries count equaling the number of list entries  1208  deleted and an appropriate response code are returned in the response operands  1014 . 
   When a model dependent time period has elapsed, the delete list entries count equaling the number of list entries  1208  deleted, the current data index of the next list entry  1208  to be processed, and an appropriate response code are returned in the response operands  1014 . When the list authority comparison, the global lock manager comparison, or the local lock manager comparison fails during the processing of a list entry  1208  other than the one specified by the starting data index, the delete list entries count equaling the number of list entries  1208  deleted, the current data index of the entry that caused the mismatch, and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the local lock managers and the local lock manager comparison fails during the processing of the entry specified by the starting data index, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock managers and the global lock manager comparison fails during the processing of the entry specified by the starting data index, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock or local lock managers, and both the global lock manager comparison and local lock manager comparison fail during the processing of the entry specified by the starting data index, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, the delete list entries count equaling the number of list entries  1208  deleted, the current data index of the nonexistent list entry  1208 , and an appropriate response code are returned in the response operands  1014 . 
   When the list authority comparison fails during the processing of the entry specified by the starting data index, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   Delete List Entry (DLE) 
   Conditionally deletes a specified list entry  1208  that matches the criteria of the version number comparison and/or key comparison requests. 
   Description: The list entry  1208  is located and, when requested, the list authorities are compared, the list numbers are compared, the version numbers are compared, the keys are compared, or the global lock managers are compared, or any combination of the preceding processes is performed. When the global lock managers are compared, the local lock managers may be compared. In order for a lock table entry  1112  to be written, all of these processes except for local lock manager comparison, when requested, must succeed. In order for the list authority to be replaced, all of these processes, when requested, must succeed. In order for a list cursor to be updated, all of these processes, when requested, must succeed. In order for a list entry  1208  to be deleted, all of these processes, when requested, must succeed. 
   When a list entry  1208  is deleted and a monitored list state transition results, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored subsidiary list state transition results, the associated event monitor controls objects  1306  are withdrawn. If this causes event queue transitions, the event queue monitors are notified. The withdrawal of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored key range state transition results, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted, the designated list entry controls, the list set entry count, the list set element count, the list entry count or list element count, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are no other local lock managers, when a local lock manager is replaced with the opposite value, or when the global lock and the local lock managers are replaced, an response code is returned in the response operand  1014 . 
   When the list authority comparison fails, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are one or more other local lock managers, or when a local lock manager is replaced with the same value, then the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When global lock manager comparison fails, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested version number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   Delete List Set (DLS) 
   Conditionally deletes all entries in the list structure  902  that match the criteria of the version number comparison and/or key comparison requests starting from a designated position specified by a restart token. Processing continues until all lists  11106  in the list structure  902  have been scanned, or a designated time period has elapsed. 
   Description: The list entries  1208  within the list set  1104  are processed starting at the entry specified by the restart token until a model dependent time period elapses or the last list entry  1208  is processed, or until an unsuccessful list authority comparison, global lock manager comparison, or local lock manager comparison occurs. A zero restart token specifies that processing starts at the beginning of the list set  1104 , and a nonzero token designates the entry for restarting the processing. 
   As part of processing each list entry  1208 , the list authority comparison, and the global lock manager comparison or the local lock manager comparison, if requested, are performed before the entry is located. If any of these comparisons fails, command execution concludes with an appropriate response code. If all of these comparisons are successful, command execution proceeds. 
   The entry is then located. To determine if the located entry is to be deleted, the version number comparison, the list number comparison, or the key comparison, or the secondary key comparison, if requested, are performed. If any of these comparisons fails, then the located entry is not deleted and command execution continues to process the next list entry  1208 . In order for the located list entry  1208  to be deleted, all of these comparisons must succeed. 
   When a list entry  1208  is deleted and a monitored list state transition results, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored subsidiary list state transition results, the associated event monitor controls objects  1306  are withdrawn. If this causes event queue transitions, the event queue monitors are notified. The withdrawal of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored key range state transition results, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When the last list entry  1208  is scanned, the delete list entries count equaling the number of list entries  1208  deleted and an appropriate response code are returned in the response operands  1014 . 
   When a model dependent time period has elapsed, the delete list entries count equaling the number of list entries  1208  deleted, the restart token designating the next list entry  1208  to be processed, and an appropriate response code are returned in the response operands  1014 . 
   When the list authority comparison, the global lock manager comparison, or the local lock manager comparison fails during the processing of a list entry  1208  other than the one specified by the restart token, the delete list entries count equaling the number of list entries  1208  deleted, the restart token designating the list entry  1208  that caused the mismatch, and an appropriate response code are returned in the response operands  1014 . 
   When the restart token operand is invalid, an appropriate response code is returned in the response operand  1014 . 
   When the LRT operand indicates to compare the local lock managers ad the local lock manager comparison fails during the processing of the entry specified by the restart token, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock managers and the global lock manager comparison fails during the processing of the entry specified by the restart token, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock or local lock managers, and both the global lock manager comparison and local lock manager comparison fail during the processing of the entry specified by the restart token, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the list authority comparison fails during the processing of the entry specified by the restart token, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   Dequeue Event Monitor Controls (DEMC) 
   Dequeues event monitor controls  1306  for a specified user from the event queue  1116  for a model dependent time period. 
   Description: The event monitor controls objects  1306  are dequeued from the event queue  1116  associated with the specified user and of the specified key type starting at the leftmost position and proceeding to the right until the model dependent time period elapses, the data area is filled, or the last event monitor controls object  1306  is dequeued. 
   The returned event monitor queued indicators are always active. 
   When an event monitor controls object  1306  is dequeued and an event queue state transition results, the event queue monitor is notified. 
   The dequeue of the event monitor controls objects  1306  and the generated list notification commands are primary processes. 
   When the last event monitor controls object  1306  is dequeued, the event monitor controls queued count is set to zero, the event monitor controls dequeued count is set to the number of event monitor controls objects  1306  dequeued and returned, and an appropriate response code are returned in the response operands  1014 . 
   When the data area is filled or a model dependent time period has elapsed, the event monitor controls queued count is set to the number of event monitor controls objects  1306  still queued, the event monitor controls dequeued count is set to the number of event monitor controls objects  1306  dequeued and returned, the dequeued event monitor controls, and an appropriate response code are returned in the response operands  1014 . 
   When the list structure  902  does not support keyed entries, the list structure type object is invalid and a request exception is recognized. 
   Deregister List Monitor (DLM) 
   Deregisters the specified list monitor. 
   Description: The deregister list monitor command deregisters the designated monitor. When an event monitor is deregistered, the designated event monitor controls object  1306  is deleted. If this causes an event queue transition, the event queue monitor is notified. The deletion of the event monitor controls object  1306  and the generated list notification commands are primary processes. 
   When the monitor is deregistered, an appropriate response code is returned in the response operand  1014 . 
   Move and Read List Entry (MRLE) 
   Reads a specified list entry  1208  that matches the input criteria and moves the entry to a target position. 
   Description: The list entry  1208  and the designated target position are located, the list entry counts or list element counts are compared, and, when requested, the list numbers are compared, the version numbers are compared, the list authorities are compared, the assignment key is updated, the keys are compared or the global lock managers are compared, or any combination of the preceding processes is performed. When the global lock managers are compared, the local lock managers may be compared. In order for a lock table entry  1112  to be written, all of these processes except for local lock manager comparison, when requested, must succeed. In order for the list authority to be replaced, all of these processes, when requested, must succeed. In order for the list cursor, version number, or assignment key to be updated, or any combination thereof, all of these processes, when requested, must succeed. In order for a list entry  1208  to be moved and read, these processes, when requested, must succeed. 
   When a list entry  1208  is moved and monitored list state transitions result, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is moved and monitored subsidiary list state transitions result, the associated event monitor controls objects  1306  are withdrawn, queued, or both. If this causes event queue transitions, the event queue monitors are notified. The withdrawal or queueing of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is moved and monitored key range state transitions result, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is moved, the designated list entry controls, the list set entry count, the list set element count, the target list entry count or list element count, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are no other local lock managers, when a local lock manager is replaced with the opposite value, or when the global lock and the local lock managers are replaced, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are one or more other local lock managers, or when a local lock manager is replaced with the same value, then the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When global lock manager comparison fails, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested version number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the list entry count matches or exceeds the list entry count limit or the list element count matches or exceeds the list element count limit, an appropriate response code is returned in the response operand  1014 . 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When updating the assignment key fails, an appropriate response code is returned in the response operand  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the designated list entry controls  1210  and an appropriate response code  12  are returned in the response operands  1014 . 
   Move List Entries (MLES) 
   Moves a set of list entries  1208  between source and target positions based on criteria in a set of move blocks. 
   
     
       
             
             
             
             
           
         
             
                 
             
             
               Move Condition 
               SMELT 
               GVNC 
               MELT 
             
             
                 
             
           
           
             
               Condition 1 
               Inactive 
               Inactive 
               B′0′ or AKRT presides over 
             
             
                 
                 
                 
               MELT 
             
             
               Condition 2 
               Inactive 
               Active 
               any value 
             
             
               Condition 3 
               Inactive 
               any value 
               B′1′ and AKRT does not preside 
             
             
               Condition 4 
               Inactive 
               any value 
               any value 
             
             
                 
             
             
               Notes:  
             
             
               1. SMELT is the secondary move entry locator type  
             
             
               2. GVNC is the granular version number control  
             
             
               3. MELT is the move entry locator type  
             
             
               4. AKRT is the assignment key request type  
             
           
        
       
     
   
   Description: When requested, the list authorities, the global lock managers, local lock managers, or any combination, are compared before the first list entry  1208  is processed. The list entries  1208  within the list set  1104  are processed starting with the list entry  1208  specified by the starting data index and continuing in the order as specified in the data block  1006 . Each list entry  1208  is located and, when requested, the version numbers are compared, the list numbers are compared, or the keys are compared, or any combination of the preceding processes is performed. In order for any list entries  1208  to be moved, the list authority comparison, and the global lock manager or local lock manager comparison, when requested, must succeed. In order for a particular list entry  1208  to be moved, the version number comparison, list number comparison, and key comparison, when requested, must succeed. 
   When the granular version number comparison flag is active, the VCRT, VRT, and CVN in the data block  1006  is used to do a version number comparison for each entry, the comparison values in the data block  1006  for the entry is used only for that list entry  1208 . When the granular version number comparison flag is active, the VN in the data block  1006  is used when the version number is replaced. When the granular version number comparison flag is inactive, the VCRT, VRT, and CVN in the MCB is tested for the list entries  1208  to be moved, and the comparison values in the MCB are used for all list entries  1208 . 
   If the halt on miscompare flag is active, the designated list entry  1208  exists but the requested version number comparison fails, the processing is stopped, the move list entries count equaling the number of list entries  1208  moved, the current data index, list entry keys if the structure is keyed and keys are assigned to the entries using assignment keys, for entries between SDX and CDX minus one, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   If the halt on miscompare flag is active, the designated list entry  1208  exists but the requested list number comparison fails, the processing is stopped, the move list entries count equaling the number of list entries  1208  moved, the current data index, list entry keys if the structure is keyed and keys are assigned to the entries using assignment keys, for entries between SDX and CDX minus one, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   If the halt on miscompare flag is active, the designated list entry  1208  exists but the requested key comparison fails, the processing is stopped, the move list entries count equaling the number of list entries  1208  moved, the current data index, list entry keys if keys are assigned to the entries using assignment keys, for entries between SDX and CDX minus one, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . When an entry is moved, the TLN value in the data block  1006  is used as the target list number to which the entry is moved. If the structure is keyed, the LEK of the list entry  1208  being moved, the TLEK in the data block  1006 , or the assignment key value are used as the primary key value in the target entry based on the MELT value and the AKRT value. When an entry is moved, the TDIR in the data block  1006  is used as the direction for the entry to be placed in the target list  1106  in primary key order. If the structure supports secondary keys, the SLEK of the list entry  1208  being moved and the TSLEK in the data block  1006  are used as the secondary key value in the target entry based on the SMELT value. When an entry is moved, the STDIR in the data block  1106  is used as the direction for the entry to be placed in the target list  1106  in secondary key order. 
   If the structure is keyed, list entry key values are returned in the MRB when assignment keys are assigned. Otherwise, the list entry key values in the MRB are reserved and have a value of zeros. 
   When a list entry  1208  is moved and a monitored list state transition results, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is moved and a monitored subsidiary list state transition results for either the source location or the target location, the associated event monitor controls objects  1306  may be withdrawn or the event monitor controls objects  1306  notified that a monitored event has occurred. If this causes event queue transitions, the event queue monitors are notified. The withdrawal or notification of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is moved and monitored key range state transitions results, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When the last list entry  1208  specified by the ending data index is processed the move list entries count, MLEC, equaling the number of list entries  1208  moved, list entry keys if the structure is keyed and keys are assigned to the entries using assignment keys, and an appropriate response code are returned in the response operands  1014 . 
   When a model dependent time period has elapsed or the LEK field in the MRB is full, the move list entries count equaling the number of list entries  1208  moved, the current data index of the next list entry  1208  to be processed, list entry keys if the structure is keyed and keys are assigned to the entries using assignment keys, for entries between SDX and CDX minus one, and an appropriate response code are returned in the response operands  1014 . 
   When the list authority comparison, the global lock manager comparison, or the local lock manager comparison fails during the processing of a list entry  1208  other than the one specified by the starting data index, the move list entries count equaling the number of list entries  1208  moved, the current data index of the entry that caused the mismatch, list entry keys if the structure is keyed and keys are assigned to the entries using assignment keys, for entries between SDX and CDX minus one, and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the local lock managers and the local lock manager comparison fails during the processing of the entry specified by the starting data index, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock managers and the global lock manager comparison fails during the processing of the entry specified by the starting data index, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock or local lock managers, and both the global lock manager comparison and local lock manager comparison fail during the processing of the entry specified by the starting data index, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When an invalid target list number is specified, the processing is stopped, the move list entries count equaling the number of list entries  1208  moved, the current data index, list entry keys if the structure is keyed and keys are assigned to the entries using assignment keys, for entries between SDX and CDX minus one, and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, then the move list entries count equaling the number of list entries  1208  moved, the current data index, list entry keys if the structure is keyed and keys are assigned to the entries using assignment keys, for entries between SDX and CDX minus one, and an appropriate response code are returned in the response operands  1014 . 
   When the list authority comparison fails during the processing of the entry specified by the starting data index, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When updating the assignment key fails, then the move list entries count equaling the number of list entries  1208  moved, the current data index, list entry keys for entries between SDX and CDX minus one, the assignment key, the assignment key threshold, and an appropriate response code is returned in the response operand  1014 . 
   When the list entry count matches or exceeds the list entry count limit, or the list element count matches or exceeds the list element count limit, then the move list entries count equaling the number of list entries  1208  moved, the current data index, list entry keys if the structure is keyed and keys are assigned to the entries using assignment keys, for entries between SDX and CDX minus one, and an appropriate response code is returned in the response operand  1014 . 
   Move List Entry (MLE) 
   Moves a specified list entry  1208  that matches the input criteria to a target position. 
   Description: The list entry  1208  and the designated target position are located, the list entry counts or list element counts are compared, and, when requested, the list numbers are compared, the version numbers are compared, the list authorities are compared, the assignment key is updated, the keys are compared, or the global lock managers are compared, or any combination of the preceding processes is performed. When the global lock managers are compared, the local lock managers may be compared. In order for a lock table entry  1112  to be written, all of these processes except for local lock manager comparison, when requested, must succeed. In order for the list authority to be replaced, all of these processes, when requested, must succeed. In order for the list cursor, version number, or assignment key to be updated, or any combination thereof, all of these processes, when requested, must succeed. In order for a list entry  1208  to be moved, all of these processes, when requested, must succeed. 
   When a list entry  1208  is moved and monitored list state transitions result, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is moved and monitored subsidiary list state transitions result, the associated event monitor controls objects  1306  are withdrawn, queued, or both. If this causes event queue transitions, the event queue monitors are notified. The withdrawal or queueing of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is moved and monitored key range state transitions result, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is moved, the designated list entry controls, the list set entry count, the list set element count, the target list entry count or list element count, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are no other local lock managers, when a local lock manager is replaced with the opposite value, or when the global lock and the local lock managers are replaced, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are one or more other local lock managers, or when a local lock manager is replaced with the same value, then the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When global lock manager comparison fails, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested version number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the list entry count matches or exceeds the list entry count limit, or the list element count matches or exceeds the list element count limit, an appropriate response code is returned in the response operand  1014 . 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When updating the assignment key fails, an appropriate response code is returned in the response operand  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   Read and Delete List Entry (RDLE) 
   Reads and deletes a specified list entry  1208  that matches the input criteria. 
   Description: The list entry  1208  is located and, when requested, the list authorities are compared, the list number is compared, the version numbers are compared, the keys are compared, or the global lock managers are compared, or any combination of the preceding processes is performed. When the global lock managers are compared, the local lock managers may be compared. In order for a lock table entry  1112  to be written, all of these processes except for local lock manager comparison, when requested, must succeed. In order for the list authority to be replaced, all of these processes, when requested, must succeed. In order for a list cursor to be updated, all of these processes, when requested, must succeed. In order for a list entry  1208  to be read and deleted, all of these processes, when requested, must succeed. 
   When a list entry  1208  is deleted and a monitored list state transition results, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored subsidiary list state transition results, the associated event monitor controls objects  1306  are withdrawn. If this causes event queue transitions, the event queue monitors are notified. The withdrawal of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is deleted and a monitored key range state transition results, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is read and deleted, the designated list entry controls, the list set entry count the list set element count, the list entry count or list element count, and an appropriate response code are return ed in the response operands  1014 . 
   When a global lock manager is replaced and there are no other local lock managers, when a local lock manager is replaced with the opposite value, or when the global lock and the local lock managers are replaced, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are one or more other local lock managers, or when a local lock manager is replaced with the same value, then the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When global lock manager comparison fails, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested version number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   Read List Entry (RLE) 
   Reads a specified list entry  1208  that matches the input criteria. 
   Description: The list entry  1208  is located and, when requested, the list authorities are compared, the list numbers are compared, the version numbers are compared, the keys are compared, or the global lock managers are compared, or any combination of the preceding processes is performed. When the global lock managers are compared, the local lock managers may be compared. In order for a lock table entry  1112  to be written, all of these processes except for local lock manager comparison, when requested, must succeed. In order for the list authority to be replaced, all of these processes, when requested, must succeed. In order for a list cursor or version number to be updated, or any combination thereof, all of these processes, when requested, must succeed. In order for a list entry  1208  to be read, all of these processes, when requested, must succeed. 
   When a list entry  1208  is read, the designated list entry controls, the list set entry count, the list set element count, the list entry count or list element count, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are no other local lock managers, when a local lock manager is replaced with the opposite value, or when the global lock and the local lock managers are replaced, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are one or more other local lock managers, or when a local lock manager is replaced with the same value, then the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When global lock manager comparison fails, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested version number comparison fails, the designated list entry controls and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the designated list entry controls and an appropriate response code are returned in the response operands  1014 . 
   Read Event Monitor Controls (REMC) 
   Reads the event monitor controls  1306  for a specified user and subsidiary list. 
   Description: The event monitor controls of the specified key type and an appropriate response code are returned in the response operands  1014 . 
   When the specified event monitor controls  1306  do not exist, an appropriate response code is returned in the response operand  1014 . 
   When the list structure  902  does not support keyed entries and the key type is primary, or the list structure  902  does not support secondary keys and the key type is secondary, the list structure type object is invalid and a request exception is recognized. 
   Read Event Monitor Controls List (REMCL) 
   Reads a range of event monitor controls  1306  into a data block  1106  for a model dependent time interval. 
   Description: The event monitor controls  1306  of the specified key type with list numbers within the range of values starting at the starting list number up to and including the ending list number are read. The event monitor controls  1306  within the list set  1104  are scanned starting with the starting list number or the EMC restart token until a model dependent time period elapses, the data block  1106  is full of event monitor controls  1306 , or the last event monitor control  1306  is scanned. A zero restart token causes the entire list  1106  to be processed starting at the starting list number operand. A valid nonzero EMC restart token starts the processing at the event monitor control object  1306  designated by the EMC restart token. 
   The EMCs are scanned starting with the starting list number, then in ascending order by LN up to the ending list number. The EMCs in a list number are scanned in an unpredictable ordering for keys, and an unpredictable ordering for UIDs within a key value. 
   When the last EMC within the list number range is processed, the EMC processed count and an appropriate response code are returned. 
   When the command times out or the data block  1006  is full, the EMC processed count, EMC restart token, and an appropriate response code is returned. 
   When the EMC restart token operand is invalid, an appropriate response code is returned in the response code operand. 
   When the product of the value of the DBS operand and 4096 is larger than the message buffer size, there is insufficient message buffer space to contain the data block  1006 . In this case, the command is completed and an appropriate response code is returned. 
   When the list structure  902  does not support keyed entries and the key type is primary, or the list structure  902  does not support secondary keys and the key type is secondary, the list structure type object is invalid and a request exception is recognized. 
   Read Event Queue Controls (REQC) 
   Reads the event queue  1116  controls for a specified user and key type. 
   Description: The event queue controls of the specified key type and an appropriate response code returned in the response operands  1014 . 
   When the list structure  902  does not support keyed entries and the key type is primary, or the list structure  902  does not support secondary keys and the key type is secondary, the list structure type object is invalid and a request exception is recognized. 
   Read List (RL) 
   Reads the list entry controls  1210 , adjunct list entry  1216 , and data list entry  1212  for each list entry  1208  in a specified list  1106  that matches the input criteria for a model dependent time interval. 
   Description: The list entries  1208  are processed starting at the designated position and proceeding in the direction specified until a model dependent time period elapses, the data area is filled, or the last list entry  1208  is processed, or until an unsuccessful list authority comparison, global lock manager comparison, or local lock manager comparison occurs. 
   The size of the message buffer is compared to the data block size before the designated list entry  1208  is processed. When requested, the list number comparison is performed as part of processing the designated list entry  1208 . If any of these comparisons fails, command execution concludes with an appropriate response code. If all of these comparisons are successful, command execution proceeds. 
   As part of processing each list entry  1208 , the list authority comparison, and the global lock manager comparison or the local lock manager comparison, if requested, are performed before the entry is located. If any of these comparisons fails, command execution concludes with an appropriate response code. If all of these comparisons are successful, command execution proceeds. 
   When the list structure  902  supports secondary keys, the list order that is followed by the scan process is determined by the list scan key type operand. When the list scan key type is primary, the scan follows primary key order. When the list scan key type is secondary, the scan follows secondary key order. 
   The entry is then located. To determine if the located entry or list entry controls  1210  is to be read, the version number comparison and key comparison, if requested, and the list entry key comparison, if requested, are performed. If any of these comparisons fails, then the located entry or list entry controls  1210  is not read and command execution continues to process the next list entry  1208 . In order for the located list entry  1208  or list entry controls  1210  to be read, all of these comparisons must succeed. 
   The list entry controls  1210  and adjunct list entry  1216  for the first list entry  1208  that is read by the command execution are placed in the message response block  1004 . The data list entry  1212  for the first list entry  1208  that is read, and all subsequent list entry controls  1210 , adjunct list entries  1216  and data list entries that are read are placed in the data block  1006 . 
   When the last list entry  1208  is scanned, the read list entries count equaling the number of data or adjunct list entries or list entry controls  1210  stored and an appropriate response code are returned in the response operands  1014 . 
   When a model dependent time period has elapsed, then the read list entries count equaling the number of data or adjunct list entries or list entry controls  1210  stored in the message response block  1004  and data block  1006 , the list entry controls  1210  of the next list entry  1208  in the sequence to be scanned and an appropriate response code are returned in the response operands  1014 . When the list authority comparison, the global lock manager comparison, or the local lock manager comparison fails during the processing of a list entry  1208  other than the designated list entry  1208 , then the read list entries count equaling the number of data or adjunct list entries or list entry controls  1210  stored in the message response block  1004  and data block  1006 , the list entry controls  1210  of the list entry  1208  that caused the mismatch and an appropriate response code are returned in the response operands  1014 . 
   When the specified data block size is not large enough to contain the information specified by the read list type for at least one list entry  1208 , an appropriate response code is returned in the response operand  1014 . 
   When the data block  1006  does not have enough space for the next entry, then the read list entries count equaling the number of data or adjunct list entries or list entry controls  1210  stored in the message response block  1004  and data block  1006 , the list entry controls  1210  of the next list entry  1208  in the sequence to be scanned and an appropriate response code are returned in the response operands  1014 . When the LRT operand indicates to compare the local lock managers and the local lock manager comparison fails during the processing of the designated list entry  1208 , the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock managers and the global lock manager comparison fails during the processing of the designated list entry  1208 , the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock or local lock managers, and both the global lock manager comparison and local lock manager comparison fail during the processing of the designated list entry  1208 , the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails during the processing of the designated list entry  1208 , the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the located entry is not deleted and command execution continues to process the next list entry  1208 . 
   Read List Set (RLS) 
   Reads the list entry controls  1210 , adjunct list entry  1216 , and data list entry  1212  for each list entry  1208  in a list structure  902  that matches the input criteria for a model dependent time interval. 
   Description: The list entries  1208  within the list set  1104  are processed starting at the entry specified by the restart token until a model dependent time period elapses, the data area is filled, or the last list entry  1208  is processed, or until an unsuccessful list authority comparison, global lock manager comparison, or local lock manager comparison occurs. A zero restart token specifies that processing starts at the beginning of the list set  1104 , and a nonzero token designates the entry for restarting the processing. 
   As part of processing each list entry  1208 , the list authority comparison, and the global lock manager comparison or the local lock manager comparison, if requested, are performed before the entry is located. If any of these comparisons fails, command execution concludes with an appropriate response code. If all of these comparisons are successful, command execution proceeds. 
   The entry is then located. To determine if the located entry or list entry controls  1210  is to be read, the version number comparison, the list number comparison, and the key comparison, if requested, are performed. If any of these comparisons fails, then the located entry or list entry controls  1210  is not read and command execution continues to process the next list entry  1208 . In order for the located list entry  1208  or list entry controls  1210  to be read, all of these comparisons must succeed. 
   The list entry controls  1210  and adjunct list entry  1216  for the first list entry  1208  that is read by the command execution are placed in the message response block  1004 . The data list entry  1212  for the first list entry  1208  that is read and all subsequent list entry controls  1210 , adjunct list entries  1216  and data list entries that are read are placed in the data block  1006 . 
   When the last list entry  1208  is processed, the read list entries count equaling the number of data or adjunct list entries or list entry controls  1210  stored and an appropriate response code are returned in the response operands  1014 . 
   When a model dependent time period has elapsed, then the read list entries count equaling the number of data or adjunct list entries or list entry controls  1210  stored in the message response block  1004  and data block  1006 , the restart token designating the next list entry  1208  to be processed, and an appropriate response code are returned in the response operands  1014 . 
   When the list authority comparison, the global lock manager comparison, or the local lock manager comparison fails during the processing of a list entry  1208  other than the one specified by the restart token, then the read list entries count equaling the number of data or adjunct list entries or list entry controls  1210  stored in the message response block  1004  and data block  1006 , the restart token designating the list entry  1208  that caused the mismatch, and an appropriate response code are returned in the response operands  1014 . 
   When the specified data block size is not large enough to contain the information specified by the read list type for at least one list entry  1208 , an appropriate response code is returned in the response operand. 
   When the restart token is invalid, an appropriate response code is returned in the response operand. 
   When the data block  1006  does not have enough space for the next entry, then the read list entries count equaling the number of data or adjunct list entries or list entry controls  1210  stored in the message response block  1004  and data block  1006 , the restart token, and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the local lock managers and the local lock manager comparison fails during the processing of the entry specified by the restart token, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock managers and the global lock manager comparison fails during the processing of the entry specified by the restart token, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the LRT operand indicates to compare the global lock or local lock managers, and both the global lock manager comparison and local lock manager comparison fail during the processing of the entry specified by the restart token, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the list authority comparison fails during the processing of the entry specified by the restart token, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   Register Event Monitors (REMS) 
   Registers a set of event monitors based on an input list of event monitor controls  1306  for a model dependent time interval. 
   Description: The registration requests are processed starting with the event monitor controls object  1306  specified by the user identifier and starting event index and continuing in the order as specified in the data block  1006 . Each requested event monitor is registered. The user identifier that processes the event monitor control object  1306  is either the UID in the MCB if the UID location bit is B‘0’ or the user identifier in the event monitor control operand from the data block  1006  if the UID location bit is B‘1’. 
   If (1) the halt register event monitors bit is active, (2) the UID location is one, (3) the attachment override control bit is active, and (4) the user identifier is not assigned or (1) the halt register event monitors bit is active, (2) the UID location is one, (3) the attachment override control bit is inactive, and (4) the user identifier is not attached, or (1) the halt register event monitors bit is active, (2) the UID location is one, (3) the user identifier is attached, and (4) the list notification token is invalid, then the processing is stopped, the current event index of the EMC that failed, the event monitor controls count, the maximum event monitor controls count, the monitored object state vector, and an appropriate response code are returned in the response operands  1014 . 
   When the attachment override control bit is active and the halt register event monitors bit is inactive, the EMC is skipped and processing continues if an EMC specifies a UID that is not assigned. When the attachment override control bit is inactive and the halt register event monitors bit is inactive, the EMC is skipped and processing continues if an EMC specifies a UID that is not attached. 
   The EMC is queued, not queued, withdrawn, or not withdrawn based on the INRT bit, EMQIC bit, and the EMQI bit. 
   When the initial notification request type operand is active, a withdrawal or queueing of the event monitor controls object  1306  associated with each request event monitor may be performed. If this causes an event queue transition, the event queue monitor is notified. The withdrawal or queueing process and the generated list notification commands are primary processes. 
   When the last event monitor specified by the ending event index is processed, the event monitor controls count, the maximum event monitor controls count, the monitored object state vector, and an appropriate response code are returned in the response operands  1014 . 
   When a model dependent time period has elapsed, the current event index of the next event to be processed, the event monitor controls count, the maximum event monitor controls count, the monitored object state vector, and an appropriate response code are returned in the response operands  1014 . 
   When event monitor registration requiring event monitor controls creation is requested and the event monitor controls object space is full, the current event index of the event currently being processed, the event monitor controls count, the maximum event monitor controls count, the monitored object state vector, and an appropriate response code are returned in the response operands  1014 . 
   When the specified list structure user is attached with a zero list notification token and the UID locator bit is zero, an appropriate response code is returned in the response operand. 
   When the list number is invalid, the current event index of the event currently being processed, the event monitor controls count, the maximum event monitor controls count, the monitored object state vector, and an appropriate response code are returned in the response operand. 
   When the key type specified in the EMC is secondary and secondary keys are not supported in the structure, the current event index of the event currently being processed, the event monitor controls count, the maximum event monitor controls count, the monitored object state vector, and an appropriate response code are returned in the response operand. 
   When the list structure  902  does not support keyed entries, the list structure type object is invalid and a request exception is recognized. 
   Register List Monitor (RLM) 
   Registers a specified monitor: list, event queue, subsidiary list, or key range. 
   Description: The register list monitor command registers the designated monitor, as specified by the monitor request type and the key type. 
   When a list monitor is registered, the list entry count or the list element count, the monitored object state, and an appropriate response code are returned in the response operands  1014 . If the initial notification request type operand is active, the list monitor is notified. The generated list notification commands are primary processes. 
   When an event queue monitor is registered, the event monitor controls queued count, the monitored object state, and an appropriate response code are returned in the response operands  1014 . If the initial notification request type operand is active, the event queue monitor is notified. The generated list notification commands are primary processes. 
   When an event monitor is registered, the event monitor controls count, the maximum event monitor controls count, the monitored object state, and an appropriate response code are returned in the response operands  1014 . If the initial notification request type operand is active, a withdrawal or queueing of the designated event monitor controls object  1306  may be performed. If this causes an event queue transition, the event queue monitor is notified. The withdrawal or queueing process and the generated list notification commands are primary processes. 
   When a key range monitor is registered, the list entry count or the list element count, the monitored object state, and an appropriate response code are returned in the response operands  1014 . If the initial notification request type operand is active, the key range monitor is notified. The generated list notification commands are primary processes. When the write event queue transition count bit is active and the monitor register type specifies register event queue monitor, The event queue transition count object is written. Otherwise, the event queue transition count object is not written. 
   When the specified list structure user is attached with a zero list notification token, an appropriate response code is returned in the response operand  1014 . 
   When event monitor registration requiring event monitor controls creation is requested and the event monitor controls object space is full, the event monitor controls count, the maximum event monitor controls count, and an appropriate response code are returned in the response operands  1014 . 
   When the monitor request type specifies a key range monitor and key range initialization is in progress, the key range monitor is not registered and an appropriate response code is returned in the response operands  1014 . 
   Write and Move List Entry (WMLE) 
   Write and moves a specified list entry  1208  that matches the input criteria to a target position. 
   Description: The designated list entry  1208  or position is located, and, when requested, the list authorities are compared, the assignment key is updated, the keys are compared, the global lock managers are compared, or the list entry  1208  is replaced or created, or any combination of the preceding processes is performed. When the global lock managers are compared, the local lock managers may be compared. When list entry creation is requested, the list set entry counts, the list set element counts, and the list entry counts or list element counts are compared. When list entry replacement is requested, the list number, the key, and version number comparisons, if requested, are compared, the list set element counts are compared, and, if the element count indicator is active, the list element counts are compared. When the global lock managers are compared, the lock table entry  1112  may be written. In order for a lock table entry  1112  to be written, all of these processes except for local lock manager comparison, when requested, must succeed. In order for the list authority to be replaced, all of these processes, when requested, must succeed. In order for a list cursor, version number, or assignment key to be updated, or any combination thereof, all of these processes, when requested, must succeed. In order for a list entry  1208  to be written and moved, all of these processes, when requested, must succeed. 
   When a list entry  1208  is written and moved and monitored list state transitions result, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is written and moved and monitored subsidiary list state transitions result, the associated event monitor controls objects  1306  are withdrawn, queued, or both. If this causes event queue transitions, the event queue monitors are notified. The withdrawal or queueing of the event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is created or moved and a monitored key range state transition results, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is written and moved, the list entry controls  1210 , the list set entry count, the list set element count, the target list entry count or list element count, the write result, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are no other local lock managers, when a local lock manager is replaced with the opposite value, or when the global lock and the local lock managers are replaced, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are one or more other local lock managers, or when a local lock manager is replaced with the same value, then the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When global lock manager comparison fails, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested version number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the list entry count matches or exceeds the list entry count limit, or the list element count matches or exceeds the list element count limit, an appropriate response code is returned in the response operand  1014 . 
   When the list set  1104  is full, and list entry creation or replacement is requested, an appropriate response code is returned in the response operand  1014 . If the requested operation is a replacement of an existing list entry  1208  and the value of the DLES request operand  1010  is smaller than or equal to the value of the DLES object in the list entry controls  1210 , the failed replacement indicator is set to active. Otherwise, the failed replacement indicator is set to inactive. 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When the list entry name already exists and list entry creation is requested, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When updating the assignment key fails, an appropriate response code is returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the program list entry identifier indicator is active, the list entry identifier in the MCB has already been assigned for the list structure  902 , and list entry creation is requested, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   Write List Controls (WLC) 
   Updates a subset of the list control objects for a specified list  1106 , where the subset of controls is determined by the value of the list control type. 
   Description: The list authority is compared to the value of the CLAU operand and replaced with the value of the LAU operand when they are equal. When the list authority comparison and replacement is successful, the write list controls command writes the list controls  1202 , controls and initializes the key range, depending on the list control type. 
   When the list empty and the list not-empty notification thresholds are updated, the resulting state of the list  1106  is determined and the list monitors are notified. The list notification commands are primary processes. 
   When the key range empty and not-empty notification thresholds are updated and key range is not being initialized, the resulting state of the key range is determined and the key range monitors are notified. The list notification commands are primary processes. 
   If the list cursor bit is active and the cursor direction type bit is inactive, the list cursor is initialized to the LEID of the leftmost list entry  1208  when the value of the CDIR operand is left to right and is initialized to the LEID of the rightmost list entry  1208  when the value of the CDIR operand is right to left, and the CDIR object is set equal to the CDIR operand. 
   If the list cursor bit is active and the cursor direction type bit is active, the LEID operand is nonzero, and the entry designated by the LEID request operand  1010  exists on the list  1106  designated by the LN operand, the list cursor object is initialized to the LEID operand value and the CDIR object is set equal to the CDIR operand. 
   If the list cursor bit is active and the cursor direction type bit is active, the LEID operand is nonzero, but the entry designated by the LEID request operand  1010  does not exist on the list  1106  designated by the LN operand, the LEID operand is invalid and an appropriate response code is returned in the response operand  1014 . 
   If the list cursor bit is active, the cursor direction type bit is active and the LEID operand is zero, the list cursor object is initialized to zero and the CDIR object is set equal to the CDIR operand. 
   When the list controls  1202  are written, an appropriate response code is returned in the response operand  1014 . 
   The key range is initialized when the key range list entry key and the key range maximum list entry key are updated. 
   When the list controls  1202  are written and the key range is initialized, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When key range initialization is not complete, and the key range list entry key and the key range maximum list entry key are updated, an appropriate response code is returned in the response operands  1014 . 
   Write List Entry (WLE) 
   Writes a specified list entry  1208  that matches the input criteria. 
   Description: The designated list entry  1208  or position is located and, when requested, the list authorities are compared, the assignment key is updated, the keys are compared, the global lock managers are compared, or the list entry  1208  is replaced or created, or any combination of the preceding processes is performed. When the global lock managers are compared, the local lock managers may be compared. When list entry creation is requested, the list set entry counts, the list set element counts, and the list entry counts or list element counts are compared. When list entry replacement is requested, the list number and version number comparisons, the key is compared, if requested, are compared, the list set element counts are compared, and, if the element count indicator is active, the list element counts are compared. When the global lock managers are compared, the lock table entry  1112  may be written. In order for a lock table entry  11112  to be written, all of these processes except for local lock manager comparison, when requested, must succeed. In order for the list authority to be replaced, all of these processes, when requested, must succeed. In order for a list cursor, version number, or assignment key to be updated, or any combination thereof, all of these processes, when requested, must succeed. In order for a list entry  1208  to be written, all of these processes, when requested, must succeed. 
   When a list entry  1208  is created and a monitored list state transition results, the list monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is created and a monitored subsidiary list state transition results, the associated event monitor controls objects  1306  are queued. If this causes event queue transitions, the event queue monitors are notified. The queueing of event monitor controls objects  1306  and the generated list notification commands are secondary processes. 
   When a list entry  1208  is created and a monitored key range state transition results, the key range monitors are notified. The generated list notification commands are secondary processes. 
   When a list entry  1208  is written, the list entry controls  1210 , the list set entry count, the list set element count, the list entry count or list element count, the write result, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are no other local lock managers, when a local lock manager is replaced with the opposite value, or when the global lock and the local lock managers are replaced, an appropriate response code is returned in the response operand  1014 . 
   When the list authority comparison fails, the list authority, the user list control, and an appropriate response code are returned in the response operands  1014 . 
   When a global lock manager is replaced and there are one or more other local lock managers, or when a local lock manager is replaced with the same value, then the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When global lock manager comparison fails, the lock table entry value and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested version number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the list entry count matches or exceeds the list entry count limit, or the list element count matches or exceeds the list element count limit, an indcative response code is returned in the response operand  1014 . 
   When the list set  1104  is full, and list entry creation or replacement is requested, an appropriate response code is returned in the response operand  1014 . 
   If the requested operation is a replacement of an existing list entry  1208  and the value of the DLES request operand  1010  is smaller than or equal to the value of the DLES object in the list entry controls  1210 , the failed replacement indicator is set to active. Otherwise, the failed replacement indicator is set to inactive. 
   When the designated list entry  1208  exists but the requested list number comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the designated list entry  1208  does not exist, an appropriate response code is returned in the response operand  1014 . 
   When the list entry name already exists and list entry creation is requested, the designated list entry controls  1210  and an appropriate response code are returned in the response operand  1014 . 
   When updating the assignment key fails, an appropriate response code is returned in the response operands  1014 . 
   When the designated list entry  1208  exists but the requested key comparison fails, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   When the program list entry identifier indicator is active, the list entry identifier in the MCB has already been assigned for the list structure  902 , and list entry creation is requested, the designated list entry controls  1210  and an appropriate response code are returned in the response operands  1014 . 
   MQSeries Shared Queue List Structure 
   Each list structure  902  created to support an MQSeries shared queue  106  is allocated with a list set  1104  where each list entry  1208  contains both an adjunct list entry  1216  and a data list entry  1212  and each list  1106  has a specified list entry count limit. In addition, a one-byte wide lock table  1110  is created where the number of lock table entries  1112  matches the number of list headers  202  (or, equivalently, lists  1106 ), making a one-to-one association between lock table entries  1112  and list headers  202 . The list entry-related commands use a single global lock manager value and global lock manager comparison and replacement rules to govern their operations. This provides basic fetch and hold/store and release serializaton primitives on each list  1106 . List authority values are used to provide state controls for each list  1106 , such as the put inhibited state for a list authority value of 1. List authority comparison operations are used to enforce the states. 
   The lists  1106  are also created with both primary and secondary keys and key range monitoring is supported with one key range for each list  1106 . In addition, list monitoring and sublist monitoring is supported and user controls  1108  are established to support notification operations. 
   MQSeries Put Processing 
   A new message  204  is put to the uncommitted portion  210  of the list header  202  assigned to the shared queue  106  by invocation of the following OS/390 service: 
   
     
       
             
             
           
             
             
           
             
             
           
             
             
           
             
             
             
             
           
             
           
         
             
                 
             
           
           
             
               ?IXLLIST 
               Entry type (New) 
             
             
                 
               ASSIGNENTRYID (pleid = Priority|STCK(8)|LN|MgrID) 
             
             
                 
               LISTNUMBER (LN) 
             
             
                 
               LOCKOPER (Not Held) 
             
             
                 
               LOCKINDEX (LN) 
             
             
                 
               CONTOKEN (Strb_Connect_Token) 
             
             
                 
               ADJUNCTAREA (=SLEK|SADE) 
             
             
                 
               ELEMNUM (parm_buffer_length/CSQE_element_size) 
             
             
                 
               Buffer (parm_buffer) 
             
             
                 
               BuffSize (buffer_size) 
             
             
                 
               Assign (key) 
             
           
        
         
             
                 
               ENTRYKEY (entry_key = 
             
           
        
         
             
                 
               X‘F6’|MgrID|Priority|UOW ID|LN|zeros) 
             
           
        
         
             
                 
               AuthCompare (Yes) 
             
             
                 
               AuthCompareType (Equal) 
             
             
                 
               AUTHCOMP (SCB_LHQC_List_Authority) 
             
             
                 
               AnsArea 
             
             
                 
               AnsLen 
             
             
                 
               RetCode 
             
             
                 
               RsnCode 
             
             
                 
               VersionUpdate (Set) 
             
           
        
         
             
                 
               NEWVERS (version_number 
               = 
               UOW ID 
             
             
                 
                 
               = 
               MgrID|STCK(7)) 
             
           
        
         
             
               Mode (SyncSuspend) 
             
             
                 
             
           
        
       
     
   
   The OS/390 service routine converts this to a Write List Entry (WLE) command with the following request operands: 
   
     
       
             
             
             
           
         
             
                 
             
             
               Acronym 
               Operand 
               Contents 
             
             
                 
             
           
           
             
               CC 
               Command code 
               Command Code for 
             
             
                 
                 
               WLE 
             
             
               SID 
               Structure identifier 
               List Structure ID for 
             
             
                 
                 
               ConToken 
             
             
               DLES 
               Data list entry size 
               ELEMNUM 
             
             
               LRT 
               Lock request type 
               Compare global lock 
             
             
                 
                 
               managers 
             
             
               CGLM 
               Comparative global lock manager 
               =B‘00’ 
             
             
               LTEN 
               Lock table entry number 
               =X‘0000’| 
             
             
                 
                 
               LISTNUMBER 
             
             
               KCT 
               Key comparison type 
               ignored 
             
             
               KRT 
               Key request type 
               ignored 
             
             
               LEK 
               List entry key 
               ENTRYKEY 
             
             
               VRT 
               Version request type 
               Set version number on 
             
             
                 
                 
               create 
             
             
               VCRT 
               Version comparison request type 
               ignored 
             
             
               VN 
               Version number 
               NEWVERS 
             
             
               CVN 
               Comparative version number 
               ignored 
             
             
               DIR 
               Direction 
               Left to right 
             
             
               ELT 
               Entry locator type 
               Ignored - locate by keyed 
             
             
                 
                 
               position is default for 
             
             
                 
                 
               create operations 
             
             
               ELKT 
               Entry locator key type 
               Locate by primary key 
             
             
               LNCT 
               List number comparison type 
               ignored 
             
             
               LCURT 
               List cursor request type 
               Do not update the list 
             
             
                 
                 
               cursor 
             
             
               LET 
               List entry type 
               Write data and adjunct 
             
             
               WRT 
               Write request type 
               Create a new list entry 
             
             
               LN 
               List number 
               LISTNUMBER 
             
             
               LEID 
               List entry 
               ASSIGNENTRYID 
             
             
               AKRT 
               Assignment key request type 
               List entry key not 
             
             
                 
                 
               assigned 
             
             
               AKUT 
               Assignment key update type 
               ignored 
             
             
               LAUCT 
               List authority comparison type 
               Compare for equal 
             
             
               LAURT 
               List authority replacement type 
               Do not replace list 
             
             
                 
                 
               authority 
             
             
               LCUT 
               List cursor update type 
               ignored 
             
             
               STDIR 
               Secondary target direction 
               Left to right 
             
             
               SKCT 
               Secondary key comparison type 
               Ignored 
             
             
               SKRT 
               Secondary key request type 
               ignored 
             
             
               UID 
               User identifier 
               ignored 
             
             
               LAU 
               List authority 
               ignored 
             
             
               CLAU 
               Comparative list authority 
               AUTHCOMP 
             
             
               AKI 
               Assignment key increment 
               ignored 
             
             
               ALE 
               Adjunct list entry 
               ADJAREA with first 
             
             
                 
                 
               32 bytes set to 0 
             
             
                 
             
           
        
       
     
   
   The message buffer address (Buffer) and length (Buffsize) are used to create a message buffer address list (MBAL) which accompanies the message command block  1002  for the Write List Entry (WLE) command to the selected coupling facility structure  902 . The coupling facility and structure identifier for the list structure  902  are obtained through controls associated with the ConToken. 
   When the coupling facility  104  receives the message command block  1002  and message address list for the Write List Entry (WLE) command, the following actions are taken.
     1. The value of AUTHCOMP is compared against the list authority object to ensure that the list  1106  is not put-inhibited. If the comparison shows the values are not equal, the command ends without creating a list entry  1208  and an appropriate response code is returned. If the comparison shows the values are equal, the command continues.   2. The value of the global lock manager field in the lock table entry  1112  associated with the list  1106  (i.e. Lock table entry number=LISTNUM) is compared against a value of zero. If the global lock manager field is not zero, the list  1106  is locked and cannot be changed. In this case the command ends without creating a list entry  1208  and an appropriate response code is returned. If the global lock manager field is zero, the command continues.   3. The list entry (or element) count limit is checked against the current list entry (or element) count to ensure that creation of a new list entry  1208  will not cause the count of list entries  1208  to exceed the limit. If this is the case, the command ends without creating a list entry  1208  and an appropriate response code is returned. If the list entry (or element) count limit is not exceeded by the creation of a list entry  1208 , the command continues.   4. Creation of a new list entry  1208  is attempted by obtaining free storage resources for the list entry controls  1210 , adjunct list entry  1216  and data list entry  1212 . The data list entry size is the value of ELEMNUM. If insufficient resources are available, the command ends without creating a list entry  1208  and an appropriate response code is returned. If storage resources are available, the list entry  1208  is created.   5. The list entry  1208  is created by writing the buffer contents (actual message) to the data list entry  1212 , setting the adjunct list entry  1216  equal to the ADJAREA, and setting the list entry controls  1210  to the input values. The list entry controls  1210  are set as follows:
       Adjunct format control is set to adjunct secondary key indicator   Data list entry size is set to the value of ELEMNUM   List entry identifier is set to the value of ASSIGNENTRYID   List entry key is set to the value of ENTRYKEY   List number is set to the value of LISTNUMBER   Version number is set to the value of NEWVERS   Secondary list entry key is set to zero.   
       6. The list entry  1208  is inserted in the target position for the primary key ordering based on the value of the list entry key.   7. The list entry  1208  is inserted in the target position for the secondary key ordering based on the value of zero. (Note that the OS/390 service sets the first 32 bytes of the adjunct area, which represents the secondary key, equal to zero.)   8. The list entry count or list element is incremented.   9. The command is completed and an appropriate response code is returned.
 
MQSeries Get Processing
   

   A message  204  is read from a nonindexed shared queue  106  by invocation of the following OS/390 service. This invocation will move the highest priority message  204  from the put queue  202  to the requesting shared queue manager  108 &#39;s uncommitted get queue  206  and read the contents into the requester&#39;s buffer. 
   
     
       
             
             
           
         
             
                 
             
           
           
             
               ?IXLLSTE 
               Request (MOVE) 
             
             
                 
               LISTNUM (Scb_Put_List_Number) 
             
             
                 
               LOCKOPER (Not Held) 
             
             
                 
               MOVETOLIST (STRB_SQM_Uncommitted_Get_List_Header) 
             
             
                 
               MOVETOKEY (TARGETENTRYKEY) 
             
             
                 
               TARGETKEY (uncommitted_getq_key) 
             
             
                 
               ENTRYTYPE (OLD) 
             
             
                 
               LOCATOR (UNKEYPOS) 
             
             
                 
               DIRECTION (HEADTOTAIL) 
             
             
                 
               KEYCOMPARE (YES) 
             
             
                 
               ENTRYKEY (Key_of_Message_to_MOVE = X‘0A0000 . . . 000’) 
             
             
                 
               KEYREQTYPE (LESSOREQUAL) 
             
             
                 
               AUTHCOMPARE (YES) 
             
             
                 
               AUTHCOMP (Scb_LHQC_List_Authority) 
             
             
                 
               AUTHCOMPTYPE (EQUAL) 
             
             
                 
               ADJAREA (Adjunct) 
             
             
                 
               ACTION (READ) 
             
             
                 
               Buffer (parm_buffer) 
             
             
                 
               BufSize (buffer_length) 
             
             
                 
               CONTOKEN (Strb_Connect_Token) 
             
             
                 
               Ansarea 
             
             
                 
               AnsLen 
             
             
                 
               Retcode 
             
             
                 
               RsnCode 
             
             
                 
               Mode (SyncSuspend) 
             
             
                 
             
           
        
       
     
   
   The OS/390 service routine converts this to a Move and Read List Entry (MRLE) command with the following request operands: 
   
     
       
             
             
             
           
         
             
                 
             
             
               Acronym 
               Operand 
               Contents 
             
             
                 
             
           
           
             
               CC 
               Command code 
               Command Code for 
             
             
                 
                 
               MRLE 
             
             
               SID 
               Structure identifier 
               List Structure ID for 
             
             
                 
                 
               ConToken 
             
             
               LRT 
               Lock request type 
               Compare global 
             
             
                 
                 
               lock managers 
             
             
               CGLM 
               Comparative global lock manager 
               =B‘00’ 
             
             
               LTEN 
               Lock table entry number 
               =X‘0000’| 
             
             
                 
                 
               LISTNUMBER 
             
             
               KCT 
               Key comparison type 
               Compare list entry 
             
             
                 
                 
               keys 
             
             
               KRT 
               Key request type 
               Compare for less 
             
             
                 
                 
               than or equal 
             
             
               LEK 
               List entry key 
               ENTRYKEY 
             
             
               VRT 
               Version request type 
               No action 
             
             
               VCRT 
               Version comparison request type 
               ignored 
             
             
               VN 
               Version number 
               ignored 
             
             
               CVN 
               Comparative version number 
               ignored 
             
             
               DIR 
               Direction 
               Right to left 
             
             
               ELT 
               Entry locator type 
               Locate entry by 
             
             
                 
                 
               unkeyed position 
             
             
               ELKT 
               Entry locator key type 
               ignored 
             
             
               LNCT 
               List number comparison type 
               Don&#39;t compare list 
             
             
                 
                 
               numbers 
             
             
               LCURT 
               List cursor request type 
               Do not update the 
             
             
                 
                 
               list cursor 
             
             
               TDIR 
               Target direction 
               Left to right 
             
             
               MELT 
               Move entry locator type 
               Set key to target list 
             
             
                 
                 
               entry key 
             
             
               TLEK 
               Target list entry key 
               TARGETKEY 
             
             
               TLN 
               Target list number 
               MOVETOLIST 
             
             
               LET 
               List entry type 
               Read data and 
             
             
                 
                 
               adjunct 
             
             
               LN 
               List number 
               LISTNUMBER 
             
             
               LEID 
               List entry 
               ignored 
             
             
               SLCCC 
               Suppress list count comparison control 
               Check list entry 
             
             
                 
                 
               count limit 
             
             
               AKRT 
               Assignment key request type 
               List entry key not 
             
             
                 
                 
               assigned 
             
             
               AKUT 
               Assignment key update type 
               ignored 
             
             
               LAUCT 
               List authority comparison type 
               Compare for equal 
             
             
               LAURT 
               List authority replacement type 
               Do not replace list 
             
             
                 
                 
               authority 
             
             
               LCUT 
               List cursor update type 
               ignored 
             
             
               STDIR 
               Secondary target direction 
               Left to right 
             
             
               SKCT 
               Secondary key comparison type 
               ignored 
             
             
               SKRT 
               Secondary key request type 
               ignored 
             
             
               MPKP 
               Maintain primary key position 
               Ignored 
             
             
               MSKP 
               Maintain secondary key position 
               ignored 
             
             
               UID 
               User identifier 
               ignored 
             
             
               LAU 
               List authority 
               ignored 
             
             
               CLAU 
               Comparative list authority 
               AUTHCOMP 
             
             
               AKI 
               Assignment key increment 
               ignored 
             
             
               SLEK 
               Secondary list entry key 
               zero 
             
             
                 
             
           
        
       
     
   
   The message buffer address (Buffer) and length (Buffsize) are used to create a message buffer address list (MBAL) which accompanies the message command block  1002  for the Move and Read List Entry (MRLE) command to the selected coupling facility structure  902 . The coupling facility and structure identifier for the list structure  902  are obtained through controls associated with the ConToken. 
   When the coupling facility  104  receives the message command block  1002  for the Move and Read List Entry (MRLE) comma nd, the following actions are taken.
     1. The value of AUTHCOMP is compared against the list authority object with the last known value of the list authority. If the comparison shows the values are not equal, the command ends without moving or reading a list entry  1208  and an appropriate response code is returned. If the comparison shows the values are equal, the command continues.   2. The value of the global lock manager field in the lock table entry  11112  associated with the list  1106  (i.e. Lock table entry number=LISTNUM) is compared against a value of zero. If the global lock manager field is not zero, the list  1106  is locked and cannot be changed. In this case the command ends without moving or reading a list entry  1208  and an appropriate response code is returned. If the global lock manager field is zero, the command continues.   3. The topmost list entry  1208  on the designated list  1106  is located and the list entry key is compared with the ENTRYKEY=X‘0A000 . . . 0’. If the list entry key is less than or equal to the ENTRYKEY value, then the list entry  1208  represents a committed message and the command continues. If the list entry key is greater than the ENTRYKEY value, then the list entry  1208  represents an uncommitted message (List entry key=X‘F6xxxxx’) and the command completes without moving or reading the list entry  1208  and an appropriate response code is returned.   4. The list entry (or element) count limit is checked against the current list entry (or element) count to ensure that moving the list entry  1208  to the target list  1106  will not cause the count of list entries  1208  to exceed the limit. If this is the case, the command ends without moving or reading the list entry  1208  and an appropriate response code is returned. If the list entry (or element) count limit is not exceeded by the movement of the list entry  1208 , the command continues   5. The list entry  1208  is removed from the source list  1106  and the list entry (or element) count for the source list  1106  is decremented.   6. The list entry  1208  is inserted in the target position for the primary key ordering for the specified target list  1106  based on the value of the target list entry key and the target direction.   7. The list entry  1208  is inserted in the target position for the secondary key ordering based on the value of zero. (Note that the OS/390 service sets the first 32 bytes of the adjunct area equal to zero.)   8. The list entry (or element) count for the target list  1106  is incremented.   9. The adjunct data is returned in the message response block  1004  and the data list entry  1212  is returned to the user&#39;s buffer.   10. The command is completed and an appropriate response code is returned.
 
GetWait Request
   

   When no committed messages  204  exist on the put list  202 , the CF Manager (a component of shared queue manager  108  as described in the referenced related application) is instructed to monitor the committed range  208  of the put list for transitions from the empty to the nonempty state by invocation of the following OS/390 service: 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               ?IXLLSTC 
               Request (MONITOR_KEYRANGE) 
             
             
                 
                 
               CONTOKEN (Strb_Connect_Token) 
             
             
                 
                 
               LISTNUM (List_Number_to_Process) 
             
             
                 
                 
               ACTION (Start) 
             
             
                 
                 
               VECTORINDEX (Scb_Put_List_Number) 
             
             
                 
                 
               DRIVEEXIT (Yes) 
             
             
                 
                 
               RETCODE 
             
             
                 
                 
               RSNCODE 
             
             
                 
                 
               ANSAREA 
             
             
                 
                 
               ANSLEN 
             
             
                 
                 
               MODE (SyncSuspend) 
             
             
                 
                 
             
           
        
       
     
   
   The OS/390 service establishes an internal bind between the CF Manager routine and the list notification vector index value equal to LISTNUM and then issues a Register List Monitor (RLM) command to the coupling facility  104  to register the CF Manager as a key range monitor for the key range associated with the put list  202 . The RLM command is issued with the following request operands: 
   
     
       
             
             
             
           
         
             
                 
             
             
               Acronym 
               Operand 
               Contents 
             
             
                 
             
           
           
             
               CC 
               Command code 
               Command Code for 
             
             
                 
                 
               RLM 
             
             
               SID 
               Structure identifier 
               List Structure ID for 
             
             
                 
                 
               ConToken 
             
             
               KT 
               Key type 
               ignored 
             
             
               MRT 
               Monitor request type 
               Register key range 
             
             
                 
                 
               monitor 
             
             
               INRT 
               Initial notification request type 
               ACTION = Start 
             
             
               ANENI 
               Aggressive not-empty notification 
               =Inactive 
             
             
                 
               indicator 
             
             
               WEQTC 
               Write event queue transition count 
               ignored 
             
             
               AOC 
               Attachment override control 
               Check for attachment 
             
             
               KRNRT 
               Key range notification request type 
               Update the vector 
             
             
                 
                 
               summaries 
             
             
               KRNEN 
               Key range notification entry 
               VECTORINDEX 
             
             
                 
               number 
             
             
               UID 
               User identifier 
               User ID for ConToken 
             
             
               LN 
               List number 
               LISTNUM 
             
             
               LEK 
               List entry key 
               ignored 
             
             
               SLEK 
               Secondary list entry key 
               ignored 
             
             
               UNC 
               User notification control 
               ignored 
             
             
               EQTC 
               Event queue transition count 
               ignored 
             
             
                 
             
           
        
       
     
   
   When the coupling facility  104  receives the message command block  1002  for the Register List Monitor (RLM) command, the following actions are taken.
     1. The attachment status of the specified user identifier is checked. The user must be attached with a nonzero list notification in the user controls  1108 . If the user is not attached the command ends in error. If the user is attached, but the list notification token is zero, the user is not registered and the command completes with an appropriate response code. If the user is validly attached, the command continues.   2. The monitor request type is decoded and indicates that the requested function is key range monitoring. If the key range for the list  1106  is in the process of being initialized, the user is not registered and the command completes with an appropriate response code. If the key range is not being initialized, then the command continues.   3. The user is registered as a key range monitor by setting the key range monitor active bit (KRMAB) to active in the entry  1302  of the key range monitor table  1204  for the specified list  1106  indexed by the UID. The entry  1302  is further initialized by storing the key range notification request type (KRNT) and the key range notification entry number (KRNEN) request operands into the table entry.   4. If the key range is not empty, a notification signal is sent to the user, specifying the list notification token in the user controls  1108 , and setting the LNEN and LNRT controls to the values of the KRNT and KRNEN objects respectively.   5. The command is completed and an appropriate response code is returned.   

   The key range for the put list  202  had been previously established by the CF Manager when the structure  902  was allocated by invocation of the following OS/390 service: 
   
     
       
             
             
           
         
             
                 
             
           
           
             
               ?IXLLSTC 
               Request (WRITE_LCONTROLS) 
             
             
                 
               CONTOKEN (parm_Connect_Token) 
             
             
                 
               LISTNUM (parm_List_Header) 
             
             
                 
               AUTHCOMP (Current_List_Authority) 
             
             
                 
               NEWAUTH (New_Authority_Value) 
             
             
                 
               KEYRANGE (SET) 
             
             
                 
               KEYRANGESTART (csqe_key_all_zeros = X‘000000......0000’) 
             
             
                 
               KEYRANGEEND (Key_Range_End = X‘09FFFFFFFF....FFFFF’) 
             
             
                 
               KEYRANGESTATE (Define) 
             
             
                 
               KREMPTY (TrigDepth = 0) 
             
             
                 
               KRNOTEMPTY (TrigDepth = 0) 
             
             
                 
               DRIVEEXIT (Yes) 
             
             
                 
               RETCODE 
             
             
                 
               RSNCODE 
             
             
                 
               ANSAREA 
             
             
                 
               ANSLEN 
             
             
                 
               MODE (SyncSuspend) 
             
             
                 
             
           
        
       
     
   
   
     
       
             
             
             
           
         
             
                 
             
             
               Acronym 
               Operand 
               Contents 
             
             
                 
             
           
           
             
               CC 
               Command code 
               Command Code for 
             
             
                 
                 
               WLC 
             
             
               SID 
               Structure identifier 
               List Structure ID for 
             
             
                 
                 
               ConToken 
             
             
               LCT 
               List control type 
               Update key range/ 
             
             
                 
                 
               thresholds 
             
             
               CDIR 
               Cursor direction 
               ignored 
             
             
               CDT 
               Cursor direction type 
               ignored 
             
             
               LN 
               List number 
               LISTNUM 
             
             
               LECL 
               List entry count limit 
               ignored 
             
             
               LEID 
               List entry identifier 
               ignored 
             
             
               CLAU 
               Comparative list authority 
               AUTHCOMP 
             
             
               LAU 
               List authority 
               NEWAUTH 
             
             
               ULC 
               User list control 
               ignored 
             
             
               AKT 
               Assignment key threshold 
               ignored 
             
             
               AK 
               Assignment key 
               ignored 
             
             
               LSTC 
               List state transition count 
               ignored 
             
             
               KRLEK 
               Key range list entry key 
               KEYRANGESTART 
             
             
               KRMLEK 
               Key range maximum list entry key 
               KEYRANGEEND 
             
             
               KRENT 
               Key range empty notification 
               KREMPTY = ‘0’ 
             
             
                 
               threshold 
             
             
               KRNENT 
               Key range not-empty not. threshold 
               KRNOTEMPTY = ‘0’ 
             
             
               LENT 
               List empty notification threshold 
               ignored 
             
             
               LNENT 
               List not-empty notification 
               Ignored 
             
             
                 
               threshold 
             
             
                 
             
           
        
       
     
   
   When the coupling facility  104  receives the message command block  1002  for the Write List Controls (WLC) command, the following actions are taken.
     1. The value of AUTHCOMP is compared against the list authority object with the last known value of the list authority. If the comparison shows the values are not equal, the command ends without updating the list controls  1202  and an appropriate response code is returned. If the comparison shows the values are equal, the value of NEWAUTH is placed in the list authority object and the command continues.   2. The list control type is decoded and it is determined that the key range and key range thresholds are to be updated and no other controls are changed.   3. The key range and key range thresholds are updated by storing the values of the KRLEK, KRMLEK, KRENT, and KRNENT operands into the list controls  1202  and initializing the key range.   4. If key range initialization completes the resulting key range state is set and the key range monitors are notified of the resulting state. The command completes after the notifications have completed and an appropriate response code is returned.   5. If key range initialization does not complete within a model dependent time period, an appropriate response code is returned. Key range initialization remains active.
 
SMQ Recovery—Deletion of Uncommitted Messages
   

   A two-phase recovery protocol is executed for any shared queue manager (SMQ)  108  that fails. A step in the second phase a recovery process deletes all uncommitted list entries  1208  written by the shared queue manager  108  that is being recovered. This is accomplished by using the new Delete List (DL) command with key range processing. The start of the range is the begin key, which is set to X‘F6’.QMID.(14 bytes of zeros) and the end key is set to X‘F6’.QMID.(14 bytes of ones). The QMID is the identifier of the failed SMQ  108  and the range identifies all possible puts to the uncommitted put queue portion  210  by the failed SMQ  108 . Specifying the range ensures that all the uncommitted message will be deleted without the recovering process needing to know the number or exact key values of list entries  1208  being deleted. 
   This function is accomplished by issuing the following OS/390 service. 
   
     
       
             
             
           
         
             
                 
             
           
           
             
               ?IXLLSTM 
               Request (DELETE_LIST) 
             
             
                 
               CONTOKEN (Strb_Connect_Token) 
             
             
                 
               LOCATOR (KEYPOS) 
             
             
                 
               LISTNUM (List_Number_to_Process) 
             
             
                 
               KEYTYPE (ENTRY) 
             
             
                 
               ENTRYKEY (begin_key = X‘F6’|QMID|0000000000...0000) 
             
             
                 
               KEYREQTYPE (Range) 
             
             
                 
               KEYCOMPARE (YES) 
             
             
                 
               KEYRANGEEND (end_key = X‘F6’|QMID|FFFFFFFF...FFFF) 
             
             
                 
               RETCODE 
             
             
                 
               RSNCODE 
             
             
                 
               ANSAREA 
             
             
                 
               ANSLEN 
             
             
                 
             
           
        
       
     
   
   The OS/390 service converts this to a Delete List (DL) command with the following request operands: 
   
     
       
             
             
             
           
         
             
                 
             
             
               Acronym 
               Operand 
               Contents 
             
             
                 
             
           
           
             
               CC 
               Command code 
               Command Code for DL 
             
             
               SID 
               Structure identifier 
               List Structure ID for 
             
             
                 
                 
               ConToken 
             
             
               LRT 
               Lock request type 
               No lock comparison 
             
             
               CGLM 
               Comparative global lock manager 
               ignored 
             
             
               LTEN 
               Lock table entry number 
               ignored 
             
             
               KCT 
               Key comparison type 
               Compare list entry keys 
             
             
               KRT 
               Key request type 
               Compare within key 
             
             
                 
                 
               range 
             
             
               LEK 
               List entry key 
               ENTRYKEY = X‘F6| 
             
             
                 
                 
               QMID|00..00’ 
             
             
               VRT 
               Version request type 
               No action 
             
             
               VCRT 
               Version comparison request type 
               ignored 
             
             
               VN 
               Version number 
               ignored 
             
             
               CVN 
               Comparative version number 
               ignored 
             
             
               DIR 
               Direction 
               Right to right 
             
             
               ELT 
               Entry locator type 
               Locate entry by keyed 
             
             
                 
                 
               position 
             
             
               ELKT 
               Entry locator key type 
               Locate by list entry key 
             
             
               LNCT 
               List number comparison type 
               Don&#39;t compare list 
             
             
                 
                 
               numbers 
             
             
               LN 
               List number 
               LISTNUMBER 
             
             
               LEID 
               List entry 
               ignored 
             
             
               LAUCT 
               List authority comparison type 
               Compare for equal 
             
             
               LSKT 
               List scan key type 
               Left to right 
             
             
               SKCT 
               Secondary key comparison type 
               ignored 
             
             
               SKRT 
               Secondary key request type 
               ignored 
             
             
               UID 
               User identifier 
               ignored 
             
             
               MLEK 
               Maximum list entry key 
               KEYRANGEEND = 
             
             
                 
                 
               X‘F6|QMID|FF....FF’ 
             
             
               CLAU 
               Comparative list authority 
               AUTHCOMP 
             
             
               MSLEK 
               Maximum secondary list entry key 
               ignored 
             
             
               SLEK 
               Secondary list entry key 
               ignored 
             
             
                 
             
           
        
       
     
   
   When the coupling facility  106  receives the message command block  1002  for the Delete List (DL) command, the following actions are taken.
     1. The value of AUTHCOMP is compared against the list authority object with the last known value of the list authority. If the comparison shows the values are not equal, the command ends without deleting a list entry  1208  and an appropriate response code is returned. If the comparison shows the values are equal, the command continues.   2. The list  1106  is searched in primary key order. The leftmost list entry  1208  within the specified key range is located and deleted from the list  1106 . The list entry count is also decremented.   3. Step  2  is repeated until either a model-dependent timeout is exceeded or all the list entries  1208  in the specified range are deleted. If a model-dependent timeout is exceeded, the command is completed and an appropriate response code is returned. If all the list entries  1208  in the specified range are deleted, an appropriate response code is returned.   

   While a particular embodiment has been shown and described, various modifications will be apparent to those skilled in the art. While the invention has particular application in a message queuing environment, it is not limited to such an environment and may be used in other environments as well.