Patent Publication Number: US-8122203-B2

Title: Serviceability level indicator processing for storage alteration

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to computers, and more particularly to apparatus, method and computer program product embodiments for implementing Serviceability Level Indicator Processing (SLIPs) for storage alteration in a computer system. 
     2. Description of the Related Art 
     Computers and computer systems are found in a variety of settings in today&#39;s society. Computing environments and networks may be found at home, at work, at school, in government, and in other settings. In many computer systems, an operating system (OS) helps to share computer resources (processor, memory, disk space, network bandwidth, etc.) between users and application programs. Operating systems may also control access to the computer system in a security-related function. 
     Generally, computing environments known as servers store data in mass storage subsystems that typically include a number of disk storage units. Data is stored in units, such as files. In a server, a file may be stored on one disk storage unit, or alternatively portions of a file may be stored on several disk storage units. A server may service access requests from a number of users concurrently, and it will be appreciated that it will be preferable that concurrently serviced access operations be in connection with information that is distributed across multiple disk storage units, so that they can be serviced concurrently. Otherwise stated, it is generally desirable to store information in disk storage units in such a manner that one disk drive unit not be heavily loaded, or busy servicing accesses, and while others are lightly loaded or idle. Operating systems may be used, along with storage-specific applications, to facilitate the data storage. 
     In some cases, various issues may arise when data is allocated, either physically or virtually, over a portion of existing data by an operating system. These storage overlay problems may be difficult to diagnose in the operating system. 
     SUMMARY OF THE INVENTION 
     In some cases, storage overlays may be observed and present problems in various operating systems. Storage overlays may cause data outages and data loss. The primary technique for debugging such storage overlays in the IBM z/OS operating system has been the use of storage alteration slips. In general, use of the term “slip” may refer to Serviceability Level Indicator Processing and the accompanying acronym (SLIP). In general, SLIP processing is a diagnostic aid that intercepts or traps certain system events. For example, it can take be used to monitor the Program Status Word (PSW) storage address to identify when a specific instruction is executed. This type of program event recording (PER) slip is limited to having one active PER slip at a given time due to hardware limitation. 
     Two unique slips are typically used to diagnose storage overlays in the z/OS operating system. As an example on how this is implemented, a first slip identifies the offset of an instruction within a program where a data area in storage is first created and used by the code. The first slip which triggered after the data area was obtained is then disabled. The second slip is then enabled using the address of the new data area as input for the beginning of a range to be monitored. The second slip will then monitor any changes to the data area for a specific range. If any application overlays the storage block with invalid data then a dump of the effected storage is taken to identify the application. 
     While the second slip may be enabled by the satisfaction of a particular condition, there currently is no automated mechanism by which if, for example, a job associated with the storage block runs to completion without error, the second slip terminates. Instead, the end user may have to manually disable the second slip and take further action. A need exists for an automatic mechanism to implement SLIP processing in computer environments to appropriately diagnose storage alterations. 
     Accordingly, in one embodiment, by way of example only, a method for implementing Serviceability Level Indicator Processing (SLIPs) for storage alterations in a computer system is provided. A plurality of storage release requests is analyzed to identify an address monitored by a storage alteration slip. Upon identification of the address, the storage alteration slip is disabled and an initialization slip is re-enabled. 
     In another embodiment, again by way of example only, a system for implementing Serviceability Level Indicator Processing (SLIPs) for storage alterations in a computer system is provided. A slip module is operational on an operating system (OS) of the computer system. The slip module is adapted for analyzing a plurality of storage release requests to identify an address monitored by a storage alteration slip, and upon identification of the address, disabling the storage alteration slip and re-enabling an initialization slip. 
     In still another embodiment, again by way of example only, a computer program product for implementing Serviceability Level Indicator Processing (SLIPs) for storage alterations in a computer system is provided. The computer program product comprises a computer-readable storage medium having computer-readable program code portions stored therein. The computer-readable program code portions include a first executable portion for analyzing a plurality of storage release requests to identify an address monitored by a storage alteration slip, and a second executable portion for, upon identification of the address, disabling the storage alteration slip and re-enabling an initialization slip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which: 
         FIG. 1  illustrates an exemplary computing environment in which aspects of the present invention may be implemented; and 
         FIG. 2  illustrates an exemplary method for implementing Serviceability Level Indicator Processing (SLIPs) for storage alterations in a computer system. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The illustrated embodiments below provide mechanisms for dynamically implementing Serviceability Level Indicator Processing (SLIPs) for storage alterations in a computer system. The mechanisms allow for automated slip processing without the necessity of manual user intervention. Throughout the following description and claimed subject matter, reference will be made to two slips implemented for storage alterations in computer systems. The first slip, as discussed previously, that identifies an address location to monitor and involves a time to start monitoring the identified address may be referred to herein as an “initialization slip,” as the first slip initializes, as part of its functionality, the monitoring process. The second slip, as discussed previously, that monitors the address location until the storage is altered (e.g., modified) may be referred to herein as a “storage alteration slip.” 
     The mechanisms described below, in part, address the limitations of the two-slip methodology discussed previously. Currently, the second slip contains no mechanism by which to terminate and reset the first slip if an associated job runs to completion without error. In such cases, the storage monitored by the second slip would be legitimately freed, since the job terminated successfully. However, a subsequent application may reuse the virtual storage address for an additional job, and the second slip (still in operation) would be erroneously triggered. The current methodology requires the end user to manually disable the second slip and re-enable the first slip after the storage address is freed or the associated job completes. 
     In light of the foregoing, the mechanisms described below, in part, address these deficiencies by enhancing the slip processing (including associated logic) so that a first, initialization slip and a second, storage alteration slip would automatically reset at appropriate times, without the necessity of user interaction as is currently the case. 
       FIG. 1  hereafter provides an example of computer environment in which the mechanisms of the following embodiments may be implemented. It should be appreciated, however, that  FIG. 1  is only exemplary and is not intended to state or imply any limitation as to the particular architectures in which the exemplary aspects of the various embodiments may be implemented. Many modifications to the architecture depicted in  FIG. 1  may be made without departing from the scope and spirit of the following description and claimed subject matter. 
       FIG. 1  illustrates an exemplary computer environment  200  that can be used to implement embodiments of the present invention. The computer  202  comprises a processor  204  and a memory  206 , such as random access memory (RAM). The computer  202  is operatively coupled to a display  222 , which presents images such as windows to the user on a graphical user interface  218 . The computer  202  may be coupled to other devices, such as a keyboard  214 , a mouse device  216 , a printer, etc. Of course, those skilled in the art will recognize that any combination of the above components, or any number of different components, peripherals, and other devices, may be used with the computer  202 . 
     Generally, the computer  202  operates under control of an operating system (OS)  208  (e.g. z/OS, OS/2, LINUX, UNIX, WINDOWS, MAC OS) stored in the memory  206 , and interfaces with the user to accept inputs and commands and to present results, for example through a graphical user interface (GUI) module  232 . In one embodiment of the present invention, the slip processing is facilitated by the z/OS operating system described previously. Although the GUI module  232  is depicted as a separate module, the instructions performing the GUI functions can be resident or distributed in the operating system  208 , the computer program  210 , or implemented with special purpose memory and processors. The computer  202  also implements a compiler  212  which allows an application program  210  written in a programming language such as COBOL, PL/1, C, C++, JAVA, ADA, BASIC, VISUAL BASIC or any other programming language to be translated into code that is readable by the processor  204 . After completion, the computer program  210  accesses and manipulates data stored in the memory  206  of the computer  202  using the relationships and logic that was generated using the compiler  212 . The computer  202  also optionally comprises an external data communication device  230  such as a modem, satellite link, ethernet card, wireless link or other device for communicating with other computers, e.g. via the Internet or other network. 
     In one embodiment, instructions implementing the operating system  208 , the computer program  210 , and the compiler  212  are tangibly embodied in a computer-readable medium, e.g., data storage device  220 , which may include one or more fixed or removable data storage devices, such as a zip drive, disc  224 , hard drive, DVD/CD-ROM, digital tape, etc., which are generically represented as the disc  224 . Further, the operating system  208  and the computer program  210  comprise instructions which, when read and executed by the computer  202 , cause the computer  202  to perform the steps necessary to implement and/or use the present invention. Computer program  210  and/or operating system  208  instructions may also be tangibly embodied in the memory  206  and/or transmitted through or accessed by the data communication device  230 . As such, the terms “article of manufacture,” “program storage device” and “computer program product” as may be used herein are intended to encompass a computer program accessible and/or operable from any computer readable device or media. 
     Embodiments of the present invention may include one or more associated software application programs  210  that include, for example, functions for managing a distributed computer system comprising a network of computing devices, such as a storage area network (SAN). The program  210  may operate within a single computer  202  or as part of a distributed computer system comprising a network of computing devices. The network may encompass one or more computers connected via a local area network and/or Internet connection (which may be public or secure, e.g. through a VPN connection), or via a fibre channel Storage Area Network or other known network types as will be understood by those skilled in the art. (Note that a fibre channel SAN is typically used only for computers to communicate with storage systems, and not with each other.) 
     Operating system  208  includes a slip module  209 . The slip module may operate in conjunction with program(s)  210 , and other components within the computer environment  200 , to implement Serviceability Level Indicator Processing (SLIPs) on the environment  200 . In one embodiment, the slip module  209  is adapted to perform various methodologies which will be further described, such as enabling or disabling the initialization slip, and enabling or disabling the storage alteration slip while re-enabling the initialization slip. As one skilled in the art will appreciate, however, various additional components of the environment  200  may work individually or in concert to define, initialize, and perform the slip functionality as will be further described. 
     In general, and in accordance with the present invention, slip processing may be enhanced with various changes. The changes may be implemented automatically without the necessity of user interaction with the environment  200 . The changes will be described in additional detail. In general, however, the changes may include monitoring functionality incorporated within the slip module that compares all storage release requests to determine if the address space monitored by the storage alteration slip is within a range of storage being freed. In other words, if a storage release request corresponds with the address space monitored by the storage alteration slip, the monitoring functionality is adapted to determine, as a result, that the storage alteration slip is no longer needed (i.e., the storage was freed by a successfully terminating job, for example). The slip module may then disable the storage alteration sip and re-enable the initialization slip. 
     In addition, during a normal operation when the initialization slip enables the storage alteration slip as a result of a satisfied condition, location information associated with the initialization slip may be saved in a control file in order for the storage alteration slip to later use the location information to reset the initialization slip. 
     Finally, the monitoring functionality in the slip module may be configured to monitor a pre-specified job name and/or address space associated with that job name. When the job terminates successfully without error, the storage associated with that job is correspondingly released. As a result, the storage alteration slip is no longer valid. The monitoring functionality of the slip module may therefore be adapted to monitor the job name and/or address space to successful termination. Upon determination of the successful termination, the monitoring functionality may then disable the storage alteration slip and re-enable the initialization slip. 
     Turning to  FIG. 2 , an exemplary method  300  is depicted for implementing Serviceability Level Indicator Processing for storage alteration in a computer system. As one skilled in the art will appreciate, various steps in the method  300  may be implemented in differing ways to suit a particular application. In addition, the described method may be implemented by various means, such as hardware, software, firmware, or a combination thereof operational on or otherwise associated with the storage environment. For example, the method may be implemented, partially or wholly, as a computer program product including a computer-readable storage medium having computer-readable program code portions stored therein. The computer-readable storage medium may include disk drives, flash memory, digital versatile disks (DVDs), compact disks (CDs), and other types of storage mediums. While the method  300  relates specifically to the depicted functionality, various steps in the method  300  may be adapted for monitoring and trapping storage in other scenarios and implementations. 
     Method  300  begins (step  302 ) by defining the initialization and storage alteration slips for a particular implementation (step  304 ). As part of the definition process, the user may designate the storage location to be monitored, and/or a time to begin monitoring the address in question. The user also, for example, may designate a particular storage condition that would satisfy the initialization slip, such as the correct filling of a storage block with data. A storage alteration slip name and a code offset may also be defined. 
     As a next step, the user may enable the initialization slip to begin the monitoring process (step  306 ). The initialization slip then checks to see if the pre-designated condition was satisfied (step  308 ). If the condition is not met (step  310 ), then the initialization slip continues to check for the condition to be satisfied, returning to step  308 . If the condition is satisfied (again, step  310 ), then the initialization slip is disabled, the storage alteration slip is enabled, and the location information is saved in a control file as described previously (step  312 ). 
     As part of the functionality of the storage alteration slip, the storage address space is monitored (step  314 ). Each storage release request is analyzed to compare the storage requested to be freed with the storage being monitored (step  314 ). If a match is not determined (step  318 ), then the method  300  continues to monitor the address space/job names to determine if the pre-specified job name has successfully concluded without error. If the job name has not been concluded to successfully terminate (step  320 ), then the system continues to monitor the address space and analyze storage requests (again, step  316 ). 
     If a storage request/storage match is determined, then the storage alteration slip is disabled (step  322 ). The initialization slip is re-enabled (step  324 ), this time with new storage information (i.e., address, job name, etc.), and the method  300  returns to performing initialization slip checks for the pre-specified condition (again, step  308 ). 
     Returning to Step  320 , similarly, if a job name is determined to successfully terminate, the system is made aware that the storage space being monitored has been successfully freed. Accordingly, the storage alteration slip is disabled (step  322 ), the initialization slip is re-enabled (again, with new information) (step  324 ), and the initialization slip monitoring process begins anew (again, step  308 ). 
     Some of the functional units described in this specification have been labeled as modules in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like. 
     Modules may also be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module. 
     Indeed, a module of executable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. 
     While one or more embodiments of the present invention have been illustrated in detail, the skilled artisan will appreciate that modifications and adaptations to those embodiments may be made without departing from the scope of the present invention as set forth in the following claims.