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PI36735: SSD BLOCKS IN ESQA NOT FREED

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Customer observed high usage of SSD blocks in ESQA associated
    with WMB. It occurs when a thread invokes CSQMLOCT to locate an
    data-conversion table, and CSQMLOCT finds that there is another
    thread already trying to load the data-conversion table (in
    this case the conversion table is for 5123 to/from 1047, which
    does not actually exist). CSQMLOCT allocates a ROB to wait for
    the data-conversion table to be loaded, and then suspends on the
    ROB, which results in CSQVSRX allocating a pause-element (SSD).
    However, after CSQMLOCT has been resumed it does not release the
    ROB, which results in the ROB storage and the pause-element
    token being leaked.
    .
    Additional keywords:
    SP245 KEY0 Subpool 245 Key 0
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 7 *
    *                 Release 0 Modification 1 and Release 1       *
    *                 Modification 0.                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: Leak of ROB control blocks and their    *
    *                      associated Pause Element's when the     *
    *                      queue manager loads conversion tables.  *
    *                      For long running applications, the      *
    *                      leak can lead to a build of SSD control *
    *                      blocks in ESQA, leading to shortages of *
    *                      common storage.                         *
    *                                                              *
    *                      In some cases abend 5C6-00E50079 can    *
    *                      also occur in CSQMCNVT.                 *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    When an application attempts a conversion for which no suitable
    conversion table is loaded, it queues a request to the
    conversion task to load the table.
    If multiple applications require the same table, only one
    request is queued, and the other tasks are suspended until the
    first task resumes them, however the ROBs used to suspend these
    additional tasks are not freed, leading to the ROBs being
    leaked. These ROB's also have associated Pause Elements, and
    consequently these are also not freed, leading to a build up of
    SSD control blocks in common storage if the application is long
    running.
    
    If STOP QMGR MODE(FORCE) is issued while a task is suspended
    waiting for a conversion table to be loaded, a timing window
    exists where a ROB can be freed prior to being resumed, leading
    to abend 5C6-00E50079 in CSQMCNVT.
    

Problem conclusion

  • CSQMLOCT is changed to correctly free the ROBs associated with
    additional tasks waiting for a table to be loaded, and to
    prevent the ROB used by the initial task being freed prior to
    being resumed during STOP QMGR MODE(FORCE) processing.
    MQMSGPROP/K
    010Y
    100Y
    CSQMCNVT
    CSQMLOCT
    

Temporary fix

  • *********
    * HIPER *
    *********
    

Comments

APAR Information

  • APAR number

    PI36735

  • Reported component name

    WMQ Z/OS V7

  • Reported component ID

    5655R3600

  • Reported release

    010

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2015-03-10

  • Closed date

    2015-03-23

  • Last modified date

    2015-05-04

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

    PI37390 UI26193 UI26194

Modules/Macros

  • CSQMCNVT CSQMLOCT
    

Fix information

  • Fixed component name

    WMQ Z/OS V7

  • Fixed component ID

    5655R3600

Applicable component levels

  • R010 PSY UI26193

       UP15/04/30 P F504 ¢

  • R100 PSY UI26194

       UP15/04/30 P F504 ¢

Fix is available

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Document Information

Modified date:
04 May 2015