IBM Support

IT24878: If a shared memory set is unavailable then the queue manager canenter an infinite loop

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APAR status

  • Closed as program error.

Error description

  • If a shared memory set is unavailable then the queue manager may
    enter an
    infinite loop when using CHLAUTH administration commands.  If
    this
    problem occurs then the IBM MQ amqzlaa0 process
    will be seen to use a large amount of CPU.
    
    Extract from a failure data capture (FDC) record that was
    generated as a result of the issue:
    
    WebSphere MQ First Failure Symptom Report
    =========================================
    Probe Id          :- XY388255
    Component         :- xcsConnectSharedMemSet
    Probe Description :- AMQ6109: An internal WebSphere MQ error has
    occurred.
    ----------------------------------------------------
    MQM Function Stack
    zlaMainThread
    zlaProcessMessage
    zlaProcessSPIRequest
    zlaSPIKernel
    zsqSPIKernel
    kpiGeneric
    kqiSetChlAuthMap
    rsxAccessCache
    xcsConnectSharedMemSet
    xcsFFST
    

Local fix

  • Restarting the queue manager will work around the problem.  It
    may be necessary to end the queue manager with the -p
    (pre-emptive) option.
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    Users who remove IBM MQ shared memory resources may be affected
    by this issue.
    
    
    Platforms affected:
    MultiPlatform
    
    ****************************************************************
    PROBLEM DESCRIPTION:
    If a shared memory segment belonging to IBM MQ was removed when
    MQ is running then the amqzlaa0 process may have entered an
    infinite loop as it attempts to access this segment.
    

Problem conclusion

  • The IBM MQ code was modified so that it does not continually
    attempt to access the shared memory resource if it does not
    exist.  Instead, an FDC record with probe RM951010 is generated
    and the following error will be seen when using CHLAUTH
    administration commands:
    
    SET CHLAUTH('*') TYPE(BLOCKADDR) ADDRLIST('xxx.xxx.xxx.xxx')
         1 : SET CHLAUTH('*') TYPE(BLOCKADDR)
    ADDRLIST('xxx.xxx.xxx.xxx')
    AMQ9774: Error accessing the Channel authentication table
    
    The queue manager should be restarted as soon as possible.  It
    is advisable to check whether the ipcrm (or host OS equivalent)
    command had recently been run by an administrator or a script,
    as MQ IPC resources should not be removed while the queue
    manager is running.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v7.5       7.5.0.9
    v8.0       8.0.0.11
    v9.0 LTS   9.0.0.6
    v9.1 CD    9.1.1
    v9.1 LTS   9.1.0.1
    
    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

    IT24878

  • Reported component name

    WEBSPHERE MQ 7.

  • Reported component ID

    5724H7240

  • Reported release

    750

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2018-04-26

  • Closed date

    2018-07-05

  • Last modified date

    2018-07-12

  • 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

    WEBSPHERE MQ 7.

  • Fixed component ID

    5724H7240

Applicable component levels



Document information

More support for: WebSphere MQ
APAR / Maintenance

Software version: 7.5

Reference #: IT24878

Modified date: 12 July 2018


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