IBM Support

IT23566: Failures of asynchronous consume operations when machine is very overloaded

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APAR status

  • Closed as program error.

Error description

  • Asynchronous consume operations fail.
    
    A queue manager agent process (amqzlaa0) might also fail
    completely, resulting in connection-broken or connection-hanging
    conditions in all other applications they were serving.
    
    FDCs appear with these details.
    - KN802020 kqiRemoveFromWaiterChainWait xecL_W_TIMEOUT
    - KN346080 kpiMQGETM
    - KN346100 kpiMQGETM
    
    And possibly also
    -  XC130004 xehExceptionHandler/xcsAllocateQuickCell SIGBUS or
    SIGSEGV
    -  XC307030 xlsRequestMutex xecL_W_SEM_OWNER_DIED
    -  ZX005035 zxcProcessChildren zrcX_AGENT_DEAD
    

Local fix

  • If using a non-default OS scheduling mode, return to the default
    mode, as this might resolve the issue.
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    This has been seen only on a Solaris system when using a
    non-default operating system scheduling mode.
    
    
    Platforms affected:
    MultiPlatform
    
    ****************************************************************
    PROBLEM DESCRIPTION:
    If there are task scheduling anomalies, or if the machine is
    massively overloaded, then there is a timing window in which an
    asynchronous consume operation will abandon waiting for a post
    that was due to be received from the putter.  In this situation
    it will mark its block of memory accordingly.
    
    This is not the defect.  The defect is that a later part of the
    MQ code (running in a subsequent asynchronous consume operation)
    should have noticed that the block was marked, and taken
    specific actions as a result.  This code behaved as expected for
    the normal MQGET case, but was not correctly coded for the
    asynchronous consume case.
    

Problem conclusion

  • The MQ code has been corrected so that the special case for
    asynchronous consume is now executed correctly.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v8.0       8.0.0.11
    v9.0 LTS   9.0.0.5
    
    The latest available maintenance can be obtained from
    'WebSphere MQ Recommended Fixes'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
    
    If the maintenance level is not yet available information on
    its planned availability can be found in 'WebSphere MQ
    Planned Maintenance Release Dates'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
    ---------------------------------------------------------------
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT23566

  • Reported component name

    IBM MQ BASE MP

  • Reported component ID

    5724H7251

  • Reported release

    800

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2017-12-22

  • Closed date

    2018-05-25

  • Last modified date

    2018-09-25

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

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

Fix information

  • Fixed component name

    IBM MQ BASE MP

  • Fixed component ID

    5724H7251

Applicable component levels

[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"8.0.0.0","Edition":"","Line of Business":{"code":"LOB36","label":"IBM Automation"}}]

Document Information

Modified date:
25 September 2018