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IZ06672: WMQ queue manager error log locking can be briefly compromised, but with typically no impact.

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APAR status

  • Closed as program error.

Error description

  • WMQ employs file locking to ensure that error messages are
    not "interleaved" when written. In a very rare circumstance,
    the locking can be briefly compromised during queue manager
    startup.
    
    This is highly unlikely to manifest as an actual problem, and
    if it does then it is limited to just causing slight
    interleaving of error messages.
    

Local fix

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    This problem is highly unlikely to occur and there is no
    significant impact if it does.
    
    It should be noted that this problem was discovered on a Linux
    system which itself has a file locking issue that is under
    investigation. The WMQ issue documented here can cause
    interleaving of file locking and unlocking within a single
    process, and it is believed that this has revealed an issue in
    either Linux, or the controller software of the attached shared
    disk on which the error logs were located. This caused a WMQ
    hang during startup. This hang went unnoticed until qmgr
    shutdown, which didn't end, and resulted in a zombie amqzmur0
    queue manager process. A process stack, and WMQ trace, revealed
    a WMQ thread waiting indefinitely for the file lock.
    
    Platforms affected:
    All Unix
    
    ****************************************************************
    PROBLEM SUMMARY:
    WMQ takes out a process local lock to ensure file locking
    operates appropriately for multiple threads writing error
    messages at the same time. However, WMQ V6 implements an error
    log "daemon" which runs in a thread parallel to various others.
    The error log daemon omits to make use of this process local
    lock during its startup when it opens the error log file, which
    for a brief instant can compromise the file locking.
    

Problem conclusion

  • Corrected the process local locking necessary to ensure sound
    use of file locking.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
                       v6.0
    Platform           Fix Pack 6.0.2.4
    --------           --------------------
    AIX                U814256
    HP-UX (PA-RISC)    U814152
    HP-UX (Itanium)    U814342
    Solaris (SPARC)    U814337
    Solaris (x86-64)   U814343
    Linux (x86)        U814336
    Linux (x86-64)     U814341
    Linux (zSeries)    U814338
    Linux (Power)      U814339
    Linux (s390x)      U814340
    
    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

    IZ06672

  • Reported component name

    WMQ LIN X86 V6

  • Reported component ID

    5724H7204

  • Reported release

    600

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2007-10-17

  • Closed date

    2007-10-30

  • Last modified date

    2007-10-30

  • 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

    WMQ LIN X86 V6

  • Fixed component ID

    5724H7204

Applicable component levels

  • R600 PSY

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Document Information

Modified date:
30 October 2007