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IV47558: DIRECT I/O NOT ENABLED WHEN WRITING TO RECOVERY LOGS ON WEBSPHERE MQ FOR LINUX

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • WebSphere MQ on Linux does not use direct I/O when writing to
    the recovery log. The expected default behavior is that direct
    I/O is used. An 'strace' of strmqm should show two opens per log
    file, one using the O_DIRECT flag, rather than a single open.
    
    For example
    23342 open("/var/mqm/log/active/S0000000.LOG",O_RDWR|O_DSYNC)=8
    23342 open("/var/mqm/log/active/S0000000.LOG",
    O_RDWR|O_DSYNC|O_DIRECT) = 9
    

Local fix

  • Direct I/O can be explicitly enabled with the following tuning
    parameter in the qm.ini as follows:
         TuningParameters:
           NoLogBuffering=TRUE
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    This issue affects users of IBM MQ on Linux platforms.
    
    Users who have deployed MQ using a log filesystem which does not
    tolerate the use of O_DIRECT should follow the guidance below to
    disable this optimization.
    
    
    
    
    Platforms affected:
    Linux (s390x),Linux (x86),Linux (x86-64)
    
    ****************************************************************
    PROBLEM SUMMARY:
    The intention of the code design was to use the O_DIRECT flag
    when opening recovery log files on Linux platforms.  The wrong
    constant was used when testing for the Linux platform and so the
    option was not enabled.
    

Problem conclusion

  • The constant was corrected so that Linux platforms would use the
    O_DIRECT flag by default when opening recovery log files.
    
    This change in behavior can be overridden by adding the
    following to the relevant qm.ini file:
    
    TuningParameters:
    NoLogBuffering=FALSE
    
    Setting this tuning parameter will cause MQ to revert to the
    old behavior.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v7.1       7.1.0.5
    v7.5       7.5.0.3
    
    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

    IV47558

  • Reported component name

    WMQ LIN X86 V7

  • Reported component ID

    5724H7224

  • Reported release

    710

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2013-08-26

  • Closed date

    2013-09-27

  • Last modified date

    2016-11-21

  • 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 V7

  • Fixed component ID

    5724H7224

Applicable component levels

  • R710 PSY

       UP

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Document Information

Modified date:
08 March 2021