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IV23042: HIGH CPU USE BY AMQZLAA0 PROCESS WHEN USING WMQ 7.0 CLASSES FOR JMS AND WMQ V6.0 STYLE QUEUED PUB/SUB.

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APAR status

  • Closed as program error.

Error description

  • A standalone WebSphere MQ classes for JMS V7.0 application is
    configured to use a MessageListener against a subscription on
    a V7.0 queue manager, using the V6 style queue
    Publish/Subscribe configuration.
    
    High CPU consumption is seen on the queue manager's host
    system.  This drops to a lower level when messages are being
    processed by the application.  A trace shows that many 2033
    (MQRC_NO_MSG_AVAILABLE) return codes are being returned by the
    queue manager in rapid succession.
    

Local fix

  • Used 7.0 style PUB/SUB.
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    This issue affects users of WebSphere MQ V7 classes for JMS
    using a configuration with the following specific combination:
    
    - Using a V6.0, V7.0, V7.1 or V7.5 WebSphere MQ classes for JMS
    and queue manager, but using V6 style queued pub/sub.
    
    - Using message listeners in a standalone WebSphere MQ classes
    for JMS application, while not running within an application
    server environment.
    
    - Selectors are being used, or sparse subscriptions are enabled.
    
    - No messages are currently available for consumption by the
    MessageListener, so the browser is waiting for suitable
    messages to arrive.
    
    Platforms affected:
    All Distributed (iSeries, all Unix and Windows) +Java +Java zOS
    ****************************************************************
    PROBLEM SUMMARY:
    When the queued publish/subscribe model is used with a JMS
    MessageListener, the expected behaviour of the listener thread
    is that it continually polls the queue containing the messages
    for the subscription, using a timeout of 5 seconds.
    
    This means that if a message has not been located on the queue
    within 5 seconds, the listener's browse will return to the
    WebSphere MQ classes for JMS, with a return code of 2033,
    'MQRC_NO_MSG_AVAILABLE', which then issues another browse with
    5 second wait.
    
    In the specific configuration described above, even though the
    wait timeout value was set to 5 seconds, the wait flag was not
    set in the WebSphere MQ classes for JMS.
    
    The result of this was that if no matching message was available
    on the queue, the browse call to the queue manager returned
    immediately with another MQRC 2033.  The WebSphere MQ classes
    for JMS then looped around again issuing another browse without
    the wait flag set, resulting in further MQRC 2033 as fast as
    the application thread and queue manager were able to process.
    
    This loop continued while there were no messages were available
    on the subscriber's queue, resulting in excessive CPU being
    consumed on both the application and queue manager systems.
    

Problem conclusion

  • As a result of the code change associated with this APAR, the
    flag indicating that the browse should wait for the specified
    5 second interval is now set when the system is configured with
    this specific setup.
    
    This results in the loop running every 5 seconds instead of as
    fast as the two sides of the system were able to process the
    requests.
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
                       v7.0
    Platform           Fix Pack 7.0.1.10
    --------           --------------------
    Windows            7.0.1.10
    AIX                7.0.1.10
    HP-UX (PA-RISC)    7.0.1.10
    HP-UX (Itanium)    7.0.1.10
    Solaris (SPARC)    7.0.1.10
    Solaris (x86-64)   7.0.1.10
    iSeries            7.0.1.10
    Linux (x86)        7.0.1.10
    Linux (x86-64)     7.0.1.10
    Linux (zSeries)    7.0.1.10
    Linux (Power)      7.0.1.10
    zOS                7.0.1.10
    
                       v7.1
    Platform           Fix Pack 7.1.0.2
    --------           --------------------
    Windows            7.1.0.2
    AIX                7.1.0.2
    HP-UX (Itanium)    7.1.0.2
    Solaris (SPARC)    7.1.0.2
    Solaris (x86-64)   7.1.0.2
    iSeries            7.1.0.2
    Linux (x86)        7.1.0.2
    Linux (x86-64)     7.1.0.2
    Linux (zSeries)    7.1.0.2
    Linux (Power)      7.1.0.2
    zOS                7.1.0.2
    
                       v6.0
    Platform           Fix Pack 6.0.2.12
    --------           --------------------
    Windows            U200331
    AIX                U842074
    HP-UX (PA-RISC)    U842208
    HP-UX (Itanium)    U842213
    Solaris (SPARC)    U842209
    Solaris (x86-64)   U842216
    iSeries            tbc_p600_0_2_12
    Linux (x86)        U842210
    Linux (x86-64)     U842215
    Linux (zSeries)    U842211
    Linux (Power)      U842212
    Linux (s390x)      U842214
    
    Platform           v7.5
    --------           --------------------
    Multiplatforms     7.5.0.1
    
    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

    IV23042

  • Reported component name

    WMQ LIN X86 V7

  • Reported component ID

    5724H7224

  • Reported release

    701

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2012-06-14

  • Closed date

    2012-06-29

  • Last modified date

    2012-06-29

  • 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

[{"Line of Business":{"code":"LOB36","label":"IBM Automation"},"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSFKSJ","label":"WebSphere MQ"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"7.0.1"}]

Document Information

Modified date:
21 April 2021