IBM Support

PI66242: Z/OS MQ V9, CUSTOMER SAW AN INCREASE OF CPU CONSUMPTION WHEN USING A SHARED QUEUE USING MQGMO_SET_SIGNAL

A fix is available

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APAR status

  • Closed as program error.

Error description

  • The customer saw an increase of CPU consumption
    when using a shared queue.  They applied the
    service parm for PM99242, which had no effect as the
    getters were using MQGMO_SET_SIGNAL rather than
    MQGMO_WAIT, and the function provided by PM99242
    only caters  for getters using MQGMO_WAIT.
    
    
    Additional Symptom(s) Search Keyword(s):
    performance
    

Local fix

  • N/A
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All users of IBM MQ for z/OS Version 9 Release 0             *
    * Modification 0.                                              *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * High number of failed MQGET requests are seen in accounting  *
    * class 3 SMF 116 records when multiple getters are waiting    *
    * for messages on a shared queue.                              *
    *                                                              *
    * The getters are using MQGMO_SET_SIGNAL or they are client    *
    * applications using SHARECNV>0 SVRCONN channels that the CHIN *
    * uses MQGMO_SET_SIGNAL internally.                            *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * N/A                                                          *
    ****************************************************************
    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

  • When a service parameter is enabled, it will cause list
    transition processing to estimate the number of messages on a
    shared queue and post a smaller subset of handles to get those
    messages. This service parameter will now consider handles using
    MQGMO_SET_SIGNAL when determining whether a subset can be
    posted.
    
    
    
    The service parameter is not appropriate in all environments,
    and should only be enabled under direction of IBM support.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PI66242

  • Reported component name

    MQ Z/OS V9

  • Reported component ID

    5655MQ900

  • Reported release

    000

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2016-07-21

  • Closed date

    2016-08-30

  • Last modified date

    2016-11-02

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

    PI65486

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

    UI40455

Modules/Macros

  • CSQMLTR0
    

Fix information

  • Fixed component name

    MQ Z/OS V9

  • Fixed component ID

    5655MQ900

Applicable component levels

  • R000 PSY UI40455

       UP16/11/02 P F610

Fix is available

  • Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.

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Document Information

Modified date:
02 November 2016