IBM Support

IT23790: Applications using asynchronous messaging may trigger high CPU usage in amqzlaa0

Subscribe to this APAR

By subscribing, you receive periodic emails alerting you to the status of the APAR, along with a link to the fix after it becomes available. You can track this item individually or track all items by product.

Notify me when this APAR changes.

Notify me when an APAR for this component changes.

 

APAR status

  • Closed as program error.

Error description

  • When using asynchronous messaging (for example the AMQSCBF
    sample supplied with MQ), the MQCB callback may enter an
    infinite
    loop.
    
    This results in no messages being consumed by the application.
     The
    amqzlaa0 process may be seen to be using a lot of CPU.
    

Local fix

  • If the application uses an MQMD version 2 then this should work
    around the problem.
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    Users of applications that use asynchronous consume with a
    version 1 MQMD and MQCBD_FULL_MSG_LENGTH set and which consume
    messages that have a version 2 MQMD with MsgFlags field set may
    be affected by this problem.
    
    
    Platforms affected:
    MultiPlatform
    
    ****************************************************************
    PROBLEM DESCRIPTION:
    An application was configured to consume messages using
    asynchronous consume with a version 1 MQMD and
    MQCBD_FULL_MSG_LENGTH in the callback descriptor.  The
    application attempted to consume a message that used an MQMD
    version 2 with the MsgFlags field set.  A bug in the IBM MQ
    asynchronous consume code caused it to enter a tight loop where
    it continually uses a smaller buffer than necessary to consume
    the message from the queue.
    
    This behaviour is seen where the size of the message is close to
    a 4096 byte boundary and where it is necessary to add an MQMDE
    to the message.  The behaviour may therefore appear to occur at
    random.
    

Problem conclusion

  • The code was modified to ensure that the buffer provided to
    consume the message is large enough in the case where it is
    necessary to add an MQMDE to the message.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v8.0       8.0.0.9
    v9.0 LTS   9.0.0.4
    
    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

    IT23790

  • 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

    2018-01-22

  • Closed date

    2018-02-26

  • Last modified date

    2018-02-26

  • 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:
26 February 2018