Patent Publication Number: US-2002004835-A1

Title: Message queue server system

Description:
RELATED APPLICATION(S)  
     [0001] This application claims the benefit of U.S. Provisional Application No. 60/209,173, filed Jun. 2, 2000, entitled “Message Director,” by Yarbrough; U.S. Provisional Patent Application No. 60/209,054, filed Jun. 2, 2000, entitled “Enhanced EET-3 Channel Adapter Card,” by Haulund et al.; and related to co-pending U.S. Patent Application, filed concurrently herewith, Attorney Docket No. 2997.1002-001, entitled “Enhanced Channel Adapter,” by Haulund et al.; the entire teachings of all are incorporated herein by reference. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] Today&#39;s computing networks, such as the Internet, have become so widely used, in part, because of the ability for the various computers connected to the networks to share data. These networks and computers are often referred to as “open systems” and are capable of sharing data due to commonality among the data handling protocols supported by the networks and computers. For example, a server at one end of the Internet can provide airline flight data to a personal computer in a consumer&#39;s home. The consumer can then make flight arrangements, including paying for the flight reservation, without ever having to speak with an airline agent or having to travel to a ticket office. This is but one scenario in which open systems are used.  
       [0003] One type of computer system that has not “kept up with the times” is the mainframe computer. A mainframe computer was at one time considered a very sophisticated computer, capable of handling many more processes and transactions than the personal computer. Today, however, because the mainframe computer is not an open system, its processing abilities are somewhat reduced in value since legacy data that are stored on tapes and read by the mainframes via tape drives are unable to be used by open systems. In the airline scenario discussed above, the airline is unable to make the mainframe data available to consumers.  
       [0004]FIG. 1 illustrates a present day environment of the mainframe computer. The airline, Airline A, has two mainframes, a first mainframe  100   a  (Mainframe A) and a second mainframe  100   b  (Mainframe B). The mainframes may be in the same room or may be separated by a building, city, state or continent.  
       [0005] The mainframes  100   a  and  100   b  have respective tape drives  105   a  and  105   b  to access and store data on data tapes  115   a  and  115   b  corresponding to the tasks with which the mainframes are charged. Respective local tape storage bins  110   a  and  110   b  store the data tapes  115   a ,  115   b.    
       [0006] During the course of a day, a technician  120   a  servicing Mainframe A loads and unloads the data tapes  115   a . Though shown as a single tape storage bin  110   a , the tape storage bin  110   a  may actually be an entire warehouse full of data tapes  115   a . Thus, each time a new tape is requested by a user of Mainframe A, the technician  120   a  retrieves a data tape  115   a  and inserts it into tape drive  105   a  of Mainframe A.  
       [0007] Similarly, a technician  120   b  services Mainframe B with its respective data tapes  115   b . In the event an operator of Mainframe A desires data from a Mainframe B data tape  115   b , the second technician  120   b  must retrieve the tape and send it to the first technician  120   a , who inserts it into the Mainframe A tape drive  105   a . If the mainframes are separated by a large distance, the data tape  115   b  must be shipped across this distance and is then temporarily unavailable by Mainframe B.  
       [0008]FIG. 2 is an illustration of a prior art channel-to-channel adapter  205  used to solve the problem of data sharing between Mainframes A and B that reside in the same location. The channel-to-channel adapter  205  is in communication with both Mainframes A and B. In this scenario, it is assumed that Mainframe A uses an operating system having a first protocol, protocol A, and Mainframe B uses an operating system having a second protocol, protocol B. It is further assumed that the channel-to-channel adapter  205  uses a third operating system having a third protocol, protocol C.  
       [0009] The adapter  205  negotiates communications between Mainframes A and B. Once the negotiation is completed, the Mainframes A and B are able to transmit and receive data with one another according to the rules negotiated.  
       [0010] In this scenario, all legacy applications operating on Mainframes A and B have to be rewritten to communicate with the protocol of the channel-to-channel adapter  205 . The legacy applications may be written in relatively archaic programming languages, such as COBOL. Because many of the legacy applications are written in older programming languages, the legacy applications are difficult enough to maintain, let alone upgrade, to use the channel-to-channel adapter  205  to share data between the mainframes.  
       [0011] Another type of adapter used to share data among mainframes or other computers in heterogeneous computing environments is described in U.S. Pat. No. 6,141,701, issued Oct. 31, 2000, entitled “System for, and Method of, Off-Loading Network Transactions from a Mainframe to an Intelligent Input/Output Device, Including Message Queuing Facilities,” by Whitney. The adapter described by Whitney is a message oriented middleware system that facilitates the exchange of information between computing systems with different processing characteristics, such as different operating systems, processing architectures, data storage formats, file subsystems, communication stacks, and the like. Of particular relevance is the family of products known as “message queuing facilities” (MQF). Message queuing facilities help applications in one computing system communicate with applications in another computing system by using queues to insulate or abstract each other&#39;s differences. The sending application “connects” to a queue manager (a component of the MQF) and “opens” the local queue using the queue manager&#39;s queue definition (both the “connect” and “open” are executable “verbs” in a message queue series (MQSeries) application programming interface [API]). The application can then “put” the message on the queue.  
       [0012] Before sending a message, an MQF typically commits the message to persistent storage, typically to a direct access storage device (DASD). Once the message is committed to persistent storage, the MQF sends the message via the communications stack to the recipient&#39;s complementary and remote MQF. The remote MQF commits the message to persistent storage and sends an acknowledgment to the sending MQF. The acknowledgment back to the sending queue manager permits it to delete the message from the sender&#39;s persistent storage. The message stays on the remote MQF&#39;s persistent storage until the receiving application indicates it has completed its processing of it. The queue definition indicates whether the remote MQF must trigger the receiving application or if the receiver will poll the queue on its own. The use of persistent storage facilitates recoverability. This is known as “persistent queue.” 
       [0013] Eventually, the receiving application is informed of the message in its local queue (i.e., the remote queue with respect to the sending application), and it, like the sending application, “connects” to its local queue manager and “opens” the queue on which the message resides. The receiving application can then execute “get” or “browse” verbs to either read the message from the queue or just look at it.  
       [0014] When either application is done processing its queue, it is free to issue the “close” verb and “disconnect” from the queue manager.  
       [0015] The persistent queue storage used by the MQF is logically an indexed sequential data set file. The messages are typically placed in the queue on a first-in, first-out (FIFO) basis, but the queue model also allows indexed access for browsing and the direct access of the messages in the queue.  
       [0016] Though MQF is helpful for many applications, current MQF and related software utilize considerable mainframe resources. Moreover, modern MQF&#39;s have limited, if any, functionality allowing shared queues to be supported.  
       [0017] Another type of adapter used to share data among mainframes or other computers in heterogeneous computing environments is described in U.S. Pat. No. 5,906,658, issued May 25, 1999, entitled “Message Queuing on a Data Storage System Utilizing Message Queueing in Intended Recipient&#39;s Queue,” by Raz. Raz provides, in one aspect, a method for transferring messages between a plurality of processes that are communicating with a data storage system, wherein the plurality of processes access the data storage system by using I/O services. The data storage system is configured to provide a shared data storage area for the plurality of processes, wherein each of the plurality of processes is permitted to access the shared data storage region.  
       SUMMARY OF THE INVENTION  
       [0018] In U.S. Pat. No. 6,141,701, Whitney addresses the problem that current MQF (message queuing facilities) and related software utilize considerable mainframe resources and costs associated therewith. By moving the MQF and related processing from the mainframe processor to an I/O adapter device, the I/O adapter device performs a conventional I/O function, but also includes MQF software, a communications stack, and other logic. The MQF software and the communications stack on the I/O adapter device are conventional.  
       [0019] Whitney further provides logic effectively serving as an interface to the MQF software. In particular, the I/O adapter device of Whitney includes a storage controller that has a processor and a memory. The controller receives I/O commands having corresponding addresses. The logic is responsive to the I/O commands and determines whether an I/O command is within a first set of predetermined I/O commands. If so, the logic maps the I/O command to a corresponding message queue verb and queue to invoke the MQF. From this, the MQF may cooperate with the communications stack to send and receive information corresponding to the verb.  
       [0020] The problem with the solution offered by Whitney is similar to that of the adapter  205  (FIG. 2) in that the legacy applications of the mainframe must be rewritten to use the protocol of the MQF. This causes a company, such as an airline, that is not in the business of maintaining and upgrading legacy software to expend resources upgrading the mainframes to work with the MQF to communicate with today&#39;s open computer systems and to share data even among their own mainframes, which does not address the problems encountered when mainframes are located in different cities.  
       [0021] The problem with the solution offered in U.S. Pat. No. 5,906,658 by Raz is, as in the case of Whitney, legacy applications on mainframes must be rewritten in order to allow the plurality of processes to share data.  
       [0022] The present invention addresses the issue of having to rewrite legacy applications in mainframes by using the premise that mainframes have certain peripheral devices. For example, mainframes have tape drives, and, consequently, the legacy applications operating on the mainframes have the ability to read and write from tape drives. Therefore, the present invention addresses the problems and shortcomings of the prior art systems by providing a message queue server that emulates a tape drive that not only supports communication between two mainframes, but also provides a gateway to open systems computers, networks, and other similar message queue servers. In short, the principles of the present invention provide protocol-to-protocol conversion from mainframes to today&#39;s computing systems in a manner that does not require businesses that own the mainframes to rewrite legacy applications to share data with other mainframes and open systems.  
       [0023] One aspect of the present invention is a system for protocol conversion. The system includes a device emulator coupled to a first device, such as a mainframe computer, having a first protocol. The system includes digital storage to temporarily store information from the first protocol. The system also includes at least one manager that (i) coordinates the transfer of the information of the first protocol between the device emulator and the digital storage and (ii) coordinates transfer of the information between the digital storage and a device having a second protocol.  
       [0024] Preferably, the device emulator is a tape drive emulator. Typically, the information is arranged in a queue in the digital storage.  
       [0025] Another aspect of the present invention includes a manager for protocol conversion. The system includes at least one I/O manager having intelligence to support states of emulation devices transceiving messages using a first protocol and an interface transceiving messages using a second protocol. The system includes at least one emulation device providing low-level control reaction to an external device adhering to the first protocol. At least one group driver is included to provide an interface between the I/O manager and the emulation device(s). In one embodiment, the emulation device emulates a tape drive.  
       [0026] Yet another aspect of the present invention is a system for mainframe-to-mainframe connectivity. The system emulates a computer peripheral that is in communication with a first mainframe. The first device emulator acts as a standard sequential storage device. The system also includes a second device emulator in communication with a second mainframe. The second device emulator also acts as a standard sequential storage device. Digital storage is coupled to the first and second device emulators to store information temporarily for the first and second device emulators. The system also includes at least one manager that (i) coordinates a first transfer of information between the first device emulator and the digital storage and (ii) coordinates a second transfer of information from the digital storage to the second device emulator. The first and second mainframes have access to the information via respective device emulators. In one embodiment, the information stored in the digital storage is arranged in a queue.  
       [0027] Yet another aspect of the present invention includes a method and apparatus for managing messages in a data storage system. The data storage system receives information that is normally contained in a standard tape label. Based on the information, a controller applies the information to a non-tape memory designated for a message queue. The controller stores messages related to the information in the memory. The controller also manages the message queue as a function of the standard tape label information. Examples of standard tape label information that is acted on by the controller include: volume serial number, data set name, expiration date, security attributes, and data characteristics.  
       [0028] The various aspects of the present invention can be used in a network environment. For example, data sharing between mainframes connected to the emulators, (e.g., tape drive emulators) can be located in a closed network containing two mainframes and the emulator protocol-to-protocol conversion system, where messages are transferred from one mainframe to the other mainframe by transferring messages to the memory supporting the emulators en route to the other mainframe.  
       [0029] In a larger networking environment, the mainframes need not be in a closed network. In such a networking environment, the system includes a device emulator connecting to the mainframes, processor for executing software servicing message queues, memory for storing the message queues, and a network interface card, such as a TCP/IP interface card connecting to a TCP/IP network to transfer the messages in a packetized manner from the first mainframe to at least one other mainframe. In other words, once the messages are in the memory supporting the device emulators, the messages can be transferred to other memories supporting other device emulators via any middleware interface, commercial or customized, to transfer the messages to the other mainframe(s). Alternatively, the messages can be transferred to any open system computer or computer network. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0030] The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
     [0031]FIG. 1 is an illustration of an environment in which mainframe computers are used with computer tapes to share data among the mainframe computers;  
     [0032]FIG. 2 is a block diagram of a prior art solution to sharing data between mainframes without having to physically transport tapes between the mainframes, as in the environment of FIG. 1;  
     [0033]FIG. 3 is a block diagram in which a mainframe is able to share data with an open system computer network via a queue server according to the principles of the present invention;  
     [0034]FIG. 4 is a detailed block diagram of the queue server of FIG. 3;  
     [0035]FIG. 5 is a block diagram of an I/O manager, employed by the queue server of FIG. 4, having a device table database;  
     [0036]FIG. 6 is an illustration of an environment in which the queue server of FIG. 3 is used by mainframes to share data; and  
     [0037]FIG. 7 is a block diagram of an environment in which mainframes are able to share data with other mainframes via the queue server of FIG. 3 over long distances through the use of wide area networks. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0038] A description of preferred embodiments of the invention follows.  
     [0039]FIG. 3 is a block diagram of a mainframe  100   a  (Mainframe A) in communication with a queue server  300  employing the principles of the present invention. The queue server  300  is in communication with a computer network  350  (e.g., the Internet) and an open system computer  345 .  
     [0040] Mainframe A has an operating system and legacy applications, such as applications written in COBOL. The operating system and legacy applications are not inherently capable of communicating with todays open systems computer networks and computers. Mainframe A, however, does have data useful to open systems and other mainframes (not shown), so the queue server  300  acts as a transfer agent between Mainframe A and computers connected to the open systems computer networks and computers.  
     [0041] To transfer data between Mainframe A and the queue server  300 , Mainframe A provides data to a channel  312 . The channel  312  includes three components: a communication link  305  and two interface cards  310 , one located at Mainframe A and the other at the queue server  300 . The interface card  310  located in the queue server may support block message transfers and non-volatile memory, as described in U.S. Provisional Patent Application No. 60/209,054, filed Jun. 2, 2000, entitled “Enhanced EET-3 Channel Adapter Card,” by Haulund et al. and co-pending U.S. Patent Application, filed concurrently herewith, entitled “,” by Haulund et. al., the entire teachings of both are incorporated herein by reference. Mainframe A also receives information from the queue server  300  over the same channel  312 . The channel  312  is basically transparent to Mainframe A and the queue server  300 .  
     [0042] Mainframes, such as Mainframe A, have traditional device peripherals that support the mainframes. For example, mainframes are capable of communicating with printers and tape drives. That means that the applications running on the operating system on Mainframe A have the “hooks” for communicating with a printer and tape drive. The queue server  300  takes advantage of this commonality among mainframes by providing an interface to the legacy applications with which they are already familiar. Here, the queue server  300  has a device emulator  315  that serves as a transceiver with the legacy applications via the channels  312 . Thus, rather than “reinventing the wheel” by providing a MQF (message queue facility) that is a stand-alone device and requires legacy applications to be rewritten to communicate with them, the queue server  300  emulates a peripheral known to mainframes.  
     [0043] In one embodiment, the device emulator  315  is composed of multiple tape drive emulators  320 . In actuality, the tape drive emulators  320  are merely software instances that interact with the interface cards  310 . The tape drive emulators  320  provide low-level control reactions that adhere to the stringent timing requirements of traditional commercial tape drives that mainframes use to read and write data. In this way, the legacy applications are under the impression that they are simply reading and writing data from and to a tape drive, unaware that the data is being transferred to computers using other protocols.  
     [0044] In practice, the data received by the tape drive emulators  320  are provided to memory  330 , as supported by a protocol transfer manager  325 . Once in memory  330 , the data provided by the legacy applications are then capable of being transferred to commercial messaging middleware  335 .  
     [0045] The commercial messaging middleware  335  is also supported by the protocol transfer manager  325 , which supports read/write transactions of the commercial messaging middleware  335  with the memory  330  and higher-level administrative activities.  
     [0046] The commercial messaging middleware  335  interfaces with an interface card  338 , such as a TCP/IP interface card, that connects to a modern computer network, such as the Internet  350 , via any type of network line  340 . For example, the network line  340  could be a fiber optic cable, local area network cable, wireless interface, etc. Further, a desktop computer  345  could be directly coupled to the commercial messaging middleware  338  via the network line  340  and TCP/IP interface card  338 .  
     [0047] In effect, the queue server  300  is solving the problem of getting data from mainframes into a standard, commercial environment that is easily accessed by today&#39;s commercial programs. The commercial programs may then use the data from the mainframes to publish, filter, or transform the data for later use by, for example, airline representatives, agents, or consumers who wish to access the data for flight planning or other reasons.  
     [0048] The queue server  300  may also act as an interface between various operating systems of mainframes. For example, a TPF (transaction processing facility) mainframe operating system used for reservations and payment transactions can transfer the TPF data to a mainframe using a VM (virtual machine) mainframe operating system or to a mainframe using the MVS (multiple virtual storage) mainframe operating system. The queue server  300  allows data flow between the various mainframes by temporarily storing data in messages in persistent message queues in the memory  330 . In other words, the memory  330  is not intended as a permanent storage location as in the case of a physical reel tape, but will retain the messages containing the data until instructed to discard them.  
     [0049] The messages stored in the memory  330  are typically arranged in a queue in the same manner as messages are stored on a tape drive because the legacy systems are already programmed to store the data in that manner. Therefore, the legacy applications on the mainframes do not need to be rewritten in any way to transmit and receive data from the memory  330 . The queue is logically an indexed sequential data set file, which may also use various queuing models, such as first-in, first out (FIFO); last-in, first out (LIFO); or priority queuing models. It should be understood that the memory  330  is very large (e.g., terabytes) to accommodate all the data that is usually stored on large computer tapes.  
     [0050] The data exchange between the mainframes can be done in near real-time or non-real time, depending on the length of the queue. For example, if the queue storing the messages has a length of one message, then the data exchange is near-real-time since the message is forwarded to the receiving mainframe once the queue is full with the one message. If the length of the queue is several hundred messages, then data from a first mainframe is written until the queue is filled, and then the data is transferred to the second mainframe in a typical tape drive-to-mainframe manner. The channel  312  typically transfers messages on a message-by-message basis. The memory  330 , however, allows storage of many messages at a time, which allows the protocol transfer manager  325  to configure the tape drive emulators  320  in a mode supporting direct memory access (DMA) transfer of messages to improve data flow in the emulator-to memory link of the data flow.  
     [0051]FIG. 4 is a detailed block diagram of the queue server  300 . The queue server  300  has (i) a front-end that includes adapter cards  310  and tape drive emulators  320 , (ii) a protocol transfer manager  325  that include software processes, and (iii) a back-end that includes networking middleware  335  and network interface card  228 , where the networking middleware  335  is connected to a network line  340  via the network interface card  338 .  
     [0052] Referring first to the front-end of the queue server  300 , the adapter cards  310  and tape drive emulators  320  compose a device emulator  315 . As shown, a single tape drive emulator  320  is coupled to and supporting a single adapter card  310 . However, because the tape drive emulator  320  is embodied as one or more software instances, there can be many tape drive emulators connecting to a single adapter card  310 , and vise-versa. The tape drive emulator  320  and I/O manager  400  support the standard, channel command words provided by legacy applications operating on a mainframe, such as Mainframe A. For example, the channel command words include read, write, mount, dismount, and other tape drive commands that are normally used to control a tape drive. In an alternative embodiment, the tape drive emulators  320  emulate a different mainframe peripheral device; in that case, the tape drive emulators  320  support a different, respective, set of command words provided by the legacy applications for communicating with that different mainframe peripheral device.  
     [0053] Referring next to the protocol transfer manager  325  of the queue server  300 , located between I/O manager  400  and the tape drive emulators  320  is at least one group driver  405 . The group drivers  405  are also software instances, as in the case of the tape drive emulators  320 . The group drivers  405  are intended to off-load some of the processing required by the I/O manager  400  so that the I/O manager does not have to interface directly with each of the tape drive emulators  320 . Each group driver  405  provides interface support for one or more associated tape drive emulator(s)  320  and the I/ 0  manager  400 . The group drivers  405  multiplex signals from the number of tape drive emulators  320  with which they are associated. Because the group drivers  405  are software instances, any number of group drivers  405  can be provided to support the tape drive emulators  320 . Similarly, because the I/O manager  400  is a software instance, there can be many I/O managers  400  operating in the queue server  300 . Thus, the protocol transfer manager  325  can be configured to provide parallel processing functionality for the mainframes and open systems being serviced.  
     [0054] It should be understood that the queue server  300  is composed of electronics that include computer processors on which the I/O manager  400 , group drivers  405 , tape drive emulators  320 , and commercial messaging middleware  335  are executed. There may be several processors for parallel or distributed processing. The queue server  300  also includes other circuitry to allow the computer processors to interface with the adapter cards  310 , memory  330 , and TCP/IP interface card  338 . The queue server  300  may include additional memory (not shown), such as RAM, ROM, and/or magnetic or optical disks to store the software listed above. The memory, both for the software and the queues is preferably local to the queue server  300 , but may be remote and accessed over a local area network or wide area network. In the case of the queues, the delay in accessing the memory will cause additional latency in transferring the messages, but will not affect the interaction with the mainframes that require rapid response to requests since the tape drive emulators  320  handle that function.  
     [0055] Within the memory  330 , the messages are stored as queues  415   a ,  415   b , . . . ,  415   n  (collectively  415 ) in a volume  410 , as in the case of a standard tape. The queues  415  are managed by using information that is normally contained in a standard tape label. For example, to build the queue name, the volume serial number and data set name is used in one embodiment. Another piece of data that is normally contained in a standard tape label is an expiration date, which allows the I/ 0  manager  400  to decide how long to retain the message queue  415  in the memory  330 . Security attributes found in a standard tape label are used by the I/ 0  manager  400  to apply security attributes to the messages in the respective queues  415 .  
     [0056] Other information contained in the standard tape label may be used by the I/ 0  manager  400  to optimize the messages in the queue based on the data characteristics of the messages. Mounting the queue, which is done by selecting the pointer (i.e., software pointer storing the hexadecimal memory location) pointing to the head of the queue, is performed by the I/O manager  400  based on receiving a volume ID or data set name request message from the Mainframe A. It should be understood that the management features based on the standard tape label information just provided is merely exemplary of the types of actions that can be performed by the I/ 0  manager  400  in managing the queues. Another feature, for example, is a tape mark action that marks an indicator within the associated message queue.  
     [0057] In operation, Mainframe A provides many commands to the queue server  300  for handling messages in queues. These commands are typical of communication with a real tape drive, but here, the tape drive emulators  320  receive the commands and either (i) provide fast response to Mainframe A in response to those commands or (ii) allow the commands to pass unfettered to the I/O manager  400  for administrative non-real-time processing. The following discussion provides write and read operations that occur during typical interaction between Mainframe A and the queue server  300 .  
     [0058] Mainframe WRITE operation—scratch tape  
     [0059] Assuming the MVS Operating System is running Mainframe A, the Tape Volume Id is specified on a JCL (Job Control Library), which runs the job in question. Mainframe A initiates the tape operation by sending an LDD CCW (Load Display Device Channel Command Word), which identifies the specific tape to be mounted and the “device” on which to mount it. From the point of view of the Mainframe A, the “device” is a tape drive, which is being emulated by the tape drive emulator  320 . This CCW (i.e., the ‘command’ sent on the channel  312 ) is received by the channel-to-channel adapter card  310  and intercepted by the tape drive emulator  320 . The tape drive emulators  320  then sends notice to the group driver  405  via an interdriver control message (MOUNT_REQUEST_RECEIVED), which contains the information sent via the channel  312 . In one embodiment, there is one message path between the tape driver  320  and the group driver  405  over which messages relating to the adapters cards  310  travel (i.e., the message path is multiplexed).  
     [0060] The group driver  405  receives the message, determines its ultimate destination (i.e., the individual application or thread controlling the specific tape drive emulator  320  and queue  415 ), and places the message into a control message for delivery to the I/O manager  400 , where the I/O manager  400  is the major component of the protocol transfer manager  325 , also referred to as a SMART (system for message addressing routing and translation).  
     [0061] The I/O manager  400  uses the Tape VolumeId contained in the message to ‘lookup’ the queue associated with the Tape VolumeId. The I/O manager  400  uses the Virtual Tape Library (VTL—an internal process within the queue server  300 ) to perform this lookup function. The VTL uses a local database, described in reference to FIG. 5, to provide a mapping between the queuing engine&#39;s (i.e., I/O manager  400  and group driver  405 ) data message queues  415  (not to be confused with internal interdriver queues, not shown, between the tape drive emulators  320  and group drivers  405 ) and the tape VolumeIds requested by the mainframe job. If the request is for a ‘scratch’ tape ID, the VTL assigns an arbitrary Id from its pool of preassigned IDs; if the request is for a specific ID, the specific ID is used. Regardless of the source, the ID is associated with a message queue (e.g., queue  415   a ). If the requested message queue  415   a  exists (i.e., the I/O manager  400  is reusing an existing queue), the requested message queue  415   a  is cleared of existing messages; otherwise, a new queue is created.  
     [0062] The queue returned is associated (sometimes referred to as ‘partnered’ or ‘married’) with the mainframe making the mount request. The I/O manager  400  then notifies the group driver  405  to ‘release’ the mainframe/channel, which has been ‘waiting’ patiently for the channel/tape drive emulator to return ‘OK’ to its mount request. The group driver  405  formats and sends an interdriver ‘release’ message to the tape driver emulator  320 , which issues the necessary channel commands to release the channel  312 , Mainframe A, and itself for further activity.  
     [0063] Mainframe A most likely next sends a tape label (three short data records containing information about the data to be written) via the channel  312  to the tape drive emulator  320 . This tape label information, packaged into an interdriver message (TAPE_LABEL_RECEIVED), is intercepted by the tape drive emulator  320  and sent to the group driver  405 . The group driver  405  passes this tape label information to the I/O manager  400 .  
     [0064] The tape label information is used to ‘name’ the associated message queue  415 . The tape label information is then attached to the message queue  415  in the same way that tape label information is attached to a real (i.e., physical) tape volume. The information in the tape label remains with the message queue  415   a  and is ‘played back’ to Mainframe A when/if the message queue  415   a  is read.  
     [0065] The I/O manager  400  notifies (‘releases’) Mainframe A by passing a message to the group driver  405 , which sends the message to the tape driver  320 , which notifies the channel  312 , etc.  
     [0066] Following the release, Mainframe A begins sending data messages as if it were sending the data messages to a real tape drive. These messages are placed, under software control, directly into the main shared memory buffer pools  330  (FIG. 3) (via hardware driven DMA—Direct Memory Access, controlled by dedicated hardware, such as IBM® EET® chips residing in the channel-to-channel adapter card  310 ), which are visible to the queue server  300  components. Preferably, data messages are not copied; only pointers to the internal shared buffers are moved as interdriver messages between the tape drive emulator  320  and group driver  405 .  
     [0067] Pointers to data messages are passed as interdriver messages from the tape drive emulator  320  to the group driver  405  and are queued to the correct I/O manager  400 . The I/O manager  400  reads the interdriver message queue (not shown), references the data message buffer (not shown), and moves the message to the associated message queue  415   a . After the queue signals to the I/O manager  400  that the message is properly safe-stored, the I/O manager  400  notifies the tape drive emulator  320 , via a message to the group driver  405 , to release the channel  312  to Mainframe A.  
     [0068] This sequence continues until Mainframe A sends a TAPEMARK (a special CCW). The tape drive emulator  320  intercepts this CCW and passes it to the I/O manager  400  as a control message via the group driver  405 . After the I/O manager  400  receives the TAPEMARK, it closes the message queue  415  and disassociates it from the tape drive emulator  420 .  
     [0069] Mainframe A next sends a trailing label followed by REWIND (and/ or UNLOAD) commands. The I/O manager is notified of the command and completes the disassociation of the tape drive emulator  320  and queue  415   a . The I/O Manager  400  then recycles the tape drive emulator  320  for another mainframe request.  
     [0070] Mainframe READ operation  
     [0071] READ operations differ very little from WRITE operations. The channel/mainframe first sends a request to mount a specific tape volume (e.g., volume  410   a ). The volume  410   a  and its associated queue  415   a  must exist. Lookup is performed by the VTL.  
     [0072] Once the I/O manager  400  associates the tape drive emulator  320  with the requested queue  415   a , it passes the information from the stored label to the tape drive emulator  320 , which presents it to the channel  312  in response to a READ CCW. (This simulates a real tape device presenting the real tape label from the tape.)  
     [0073] Once Mainframe A has ‘read’ and verified the label, it sends a series of READ CCWs. These are passed to the I/O manager  400  as control messages. Each read results in the I/O manager&#39;s  400  presenting the ‘next’ data message from the queue  415   a  to the tape drive emulator  320  for delivery to the channel  312 .  
     [0074] When the last message is read from the queue  415   a , the I/O manager  400  notifies the tape drive emulator  320 , via a WRITE_TAPEMARK control command, and the tape drive emulator  320  simulates a TAPEMARK status to the channel  312 . Mainframe A then initiates ‘close’ processing during which the I/O manager  400  disassociates the queue  410   a  and tape drive emulator  320 .  
     [0075] Mainframe A then sends a REWIND or UNLOAD command via the channel  312 . This is passed to the I/O manager  400 , which completes the tape drive emulator  320  and queue  410   a  disassociation.  
     [0076] At that time, the tape drive emulator  320  enters an idle state and is available to be associated with another queue (e.g., queue  410   b ).  
     [0077]FIG. 5 is a block diagram of the I/O manager  400  and its associated device table database  500 . The device table database  500  is used to initialize various components in the queue server  300 . The device table database  500  includes a device name field, operation mode field, default channel configuration, queue name, file pointer name (pName), etc. These fields are (i) representative of the types of actions executed by a real tape drive and (ii) associated with actions requested of a real tape drive. The state of the fields in the device table database  500  configure the tape drive emulator  325  for interfacing with the commands/requests from the legacy applications in Mainframe A. Timing specifications, block size, date, time, labeled/not labeled, channel status, and other relevant information specific to the mainframes, mainframe operating system, or legacy applications are stored so as to respond to signals from the adapter cards  310  in a manner expected by the channels  312  and mainframes  100 . The device table database  500  may also include information for configuring the adapter cards  310 . Further, the device table database may include information for interfacing with the networking middleware  335  and/or TCP/IP card  338 .  
     [0078] The device table database  500  is typically accessed during initialization of the queue server  300 . For example, the device table database  500  may specify the number of tape drive emulators  320  that are used in the queue server  300  to support the adapter cards  310 , the number of group drivers supporting the I/O manager  400  in communicating with the tape drive emulators  320 , and the number of I/O managers  400  used by the queue server  300 . The device table database  500  may also specify the locations of the volumes  410  within the memory  330  and queues  405  within the volumes  410  (FIG. 4). It should be understood that the device table database  500  can be expanded and upgraded, as necessary.  
     [0079]FIG. 6 is a block diagram of a closed network  600  in which the queue server  300  is used to provide protocol conversion among four mainframes. As shown, Mainframes A-D have channels coupling them to the queue server  300 .  
     [0080] A queue  410  has been set up to store messages from Mainframe D. Following Mainframe D message storage, Mainframe A requests the messages in the queue  410 .  
     [0081] Alternatively, Mainframe A may have requested data that the I/O manager  400  knows to be stored on a Mainframe D tape. The I/O manager may cause a message to be displayed to a technician to have the data loaded by Mainframe D and stored to a message queue  410  for retrieval by Mainframe A.  
     [0082] In operation, Mainframe D writes data to the queue  410  in a manner typical of writing to a tape drive. Mainframe A reads the messages in the queue  410  in a manner typical of reading from a tape in a tape drive. As described above, the I/O manager  400  (FIG. 4) and group drivers  405  (FIG. 4) support the tape drive emulators  320  during the read and write processes. Thus, protocol A operating in Mainframe A receives data from protocol D in Mainframe D without having to rewrite legacy applications in either mainframe. This protocol conversion is supported by the commonality of the mainframes to interface with a tape drive, but which is supported by the emulation of a tape drive by the queue server  300 . Note that if the length of the queue  410  is reduced to having a length of one message, then the protocol conversion from protocol D to protocol A is near real-time.  
     [0083]FIG. 7 is a block diagram of an exemplary open network  700  having several queue servers  300  supporting mainframes in various cities about the United States. The application here is an airline, Airline A, that wishes to make its mainframe data available to other mainframes around the country for various offices of airline representatives, agents, and consumers having connections to the open network  700 .  
     [0084] In the open network  700 , in Boston, Airline A has two mainframes  100   a ,  100   b , connected to a queue server  300 . As described above, the mainframes  100   a ,  100   b , can share each other&#39;s data through the use of the associated queue server. Similarly, the mainframes  100   a ,  100   b  can share data with other mainframes via the queue server  300  and networking middleware  335  (FIG. 3). The queue server  300  is connected to a wide area network  350 . The wide area network  350  is connected to another wide area network  350  (e.g., the Internet) and another queue server  300 , which is located in New York.  
     [0085] The queue server  300  located in New York supports an associated mainframe  100   e , which is owned by Airline B. Airline B, may, for instance, be a subsidiary of Airline A or a business partner, such as an independent, international, airline affiliate. Personnel associated with Airline B may wish to access data from Airline A, such as passenger route information, transaction reports, etc.  
     [0086] Airline A also has a mainframe  100   c  in Chicago having an associated queue server  300  that provides connections to the wide area network  350 , which provides connection to the queue server  300  in New York and distal connection to the queue server  300  in Boston. In this way, personnel in Chicago connected to the Chicago mainframe  100   c  have access to data in Boston and New York. Similarly, the personnel in Chicago have access to data stored on tapes or in the mainframes located in Denver, mainframe  100   d , and Los Angeles, mainframe  100   f.    
     [0087] In effect, the queue servers  300  provide protocol-to-protocol conversion between the protocols of operating systems running the mainframes  100   a ,  100   b  and network protocols, such as the TCP/IP protocols. Commercial subsystems are used where appropriate (e.g., commercial messaging middleware  335  and TCP/IP interface card  338 ) within the queue servers  300  so as to have the queue servers  300  be compatible with the latest and/or legacy open systems architectures.  
     [0088] While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.