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IT17605: Browser client MQGETs or async consumers do not see their message until the end of their wait interval

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APAR status

  • Closed as program error.

Error description

  • If multiple client browser MQGETs are waiting for a message,
    with SHARECNV>0 then only one of them returns immediately from
    the MQGET.  The others wait within their MQGET until their
    WaitInterval is finished, and then their MQGET returns to the
    application with the message.
    
    The message should have been made available to the other
    application(s) immediately.  That is, their MQGET calls should
    have returned immediately, not after their WaitInterval had
    expired.
    
    The same effect is seen when using async consume MQ APIs (MQCB,
    MQCTL) and using a wait interval.
    
    After this, if another message arrives, then again one of the
    waiting browser MQGETs will return immediately, but the others
    will not see it till later.  In each case, even though all
    waiting browse MQGETs were eligible to receive the message
    immediately, only one of them received it immediately.  The
    others received it later.
    

Local fix

  • Set attribute SHARECNV of the server connection channel in use
    to 0, SHARECNV(0).
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    Applications performing browsing MQGETs from client programs
    connected via SHARECNV>0 channels, and using a WaitInterval.
    Also applications using asynchronous consume APIs and using a
    WaitInterval.
    
    
    Platforms affected:
    MultiPlatform
    
    ****************************************************************
    PROBLEM DESCRIPTION:
    The list of asynchronous browsing waiters within the queue
    manager was re-ordered to try to ensure fair division of work
    between them.  However, upon moving the first browsing waiter to
    the end of the list, the loop then immediately ended because the
    MQ code did not remember that there were other waiters in the
    list.  Therefore the other waiters were not considered eligible
    for posting to see that message immediately.
    

Problem conclusion

  • The coding error has been fixed so that the loop will continue,
    and consider all waiters in the case where the first one has
    been re-ordered in the list.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v7.5       7.5.0.8
    v8.0       8.0.0.7
    v9.0 CD    9.0.3
    v9.0 LTS   9.0.0.2
    
    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

    IT17605

  • Reported component name

    WEBSPHERE MQ 7.

  • Reported component ID

    5724H7240

  • Reported release

    750

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2016-10-21

  • Closed date

    2017-04-18

  • Last modified date

    2017-04-18

  • 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

  • R750 PSY

       UP



Document information

More support for: WebSphere MQ
APAR / Maintenance

Software version: 7.5

Reference #: IT17605

Modified date: 18 April 2017


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