IBM Support

PM99242: WMQ Z/OS ACCOUNTING STATS SHOW MANY EMPTY GETS, COMPARED TO VALID GETS FOR SHARED QUEUE PROCESSING.

A fix is available

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APAR status

  • Closed as program error.

Error description

  • The customer reported the following:
    MQ accounting statistics show that there are many empty gets
    (2M) compared to the amount of valid gets (30K)
    (valid get = get ending with message retrieval)
    .
    It was found that this behavior was associated with applications
    using WMQ Shared Queues.
    .
    Additional keywords:
    structure CF coupling facility QSG
    WQST fields VALIDGET GETN
    

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: High number of failed MQGET requests    *
    *                      seen in accounting class 3 SMF 116      *
    *                      records when multiple getters are       *
    *                      waiting for messages on a shared queue. *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    When 1 or more messages arrive on a shared queue all handles
    waiting for a message on that queue are posted by the list
    transition exits. If there are more handles than messages on the
    queue, some of the handles will not find a message and will
    reenter a getwait state.
    In certain environments it is possible to post a subset of the
    handles, reducing the number of additional get requests that
    are unable to successfully get a message.
    

Problem conclusion

  • A service parameter is added that when enabled will cause list
    transition processing to estimate the number of messages on a
    shared queue and post a smaller subset of getwaiters to get
    those messages.
    The service parameter is not appropriate in all environments,
    and should only be enabled under direction of IBM support.
    010Y
    100Y
    CSQMGET
    CSQMLTR0
    CSQM1PAW
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM99242

  • Reported component name

    WMQ Z/OS V7

  • Reported component ID

    5655R3600

  • Reported release

    010

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2013-10-16

  • Closed date

    2014-03-25

  • Last modified date

    2021-02-25

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

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

    UI16373 UI16374

Modules/Macros

  • CSQMGET  CSQMLTR0 CSQM1PAW
    

Fix information

  • Fixed component name

    WMQ Z/OS V7

  • Fixed component ID

    5655R3600

Applicable component levels

  • R010 PSY UI16373

       UP14/04/23 P F404

  • R100 PSY UI16374

       UP14/04/23 P F404

Fix is available

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[{"Business Unit":{"code":"BU054","label":"Systems w\/TPS"},"Product":{"code":"SG19M","label":"APARs - z\/OS environment"},"Platform":[{"code":"PF054","label":"z\/OS"}],"Version":"7.0.1"}]

Document Information

Modified date:
27 February 2021