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PH26279: MQRC_LOCAL_UOW_CONFLICT MAY LEAD TO AN ABEND0C4 IN THE WEBSPHERE SERVANT AND A HANG CAUSED BY A LOOP IN CSQ3RRSM

A fix is available

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APAR status

  • Closed as program error.

Error description

  • A WebSphere Application Server (WAS) log contains error:
    JMSCMQ0001: WEBSPHERE MQ CALL FAILED WITH REASON '2352'
    ('MQRC_LOCAL_UOW_CONFLICT')
    
    A timing window is exposed by tasks that are attempting to
    switch to an incorrect context and failing with
    MQRC_LOCAL_UOW_CONFLICT reason 2352.
    
    CSQMCPRH expresses interest in the provided context and
    determines that the context is already associated with another
    task - this is unexpected and correctly results in the
    MQRC_LOCAL_UOW_CONFLICT error being returned. However if that
    specific context is being committed at the same time, an error
    in serialization of the context ACE between CSQMCPRH and
    CSQ3RRSM (the RRS exit performing the commit) can lead to the
    0C4 in CSQ3RRSM seen in the initial dump.  The dump title says
    M=CSQ3RRSF, but the PSW is in CSECT CSQ3RRSM.
    
    If CSQ3RRSM is driven from a different home address space than
    CSQMCPRH is running under (in the dump, CSQ3RRSM had been
    invoked from a TCB in the RRS address space rather than one in
    the Servant region address space), the context ACE can be left
    on the VLCAAACE chain for the servant region following recovery
    for the 0C4, resulting in other potential errors, including a
    loop in the chain such as the one that was preventing the
    servant region shutting down.
    
    The stack associated with the ABEND0C4:
    Native traceback:
    __zerro   +0000120C
    __zerros  +00000306
    CEEHDSP   +000044AE
    CEEOSIGJ  +00000962
    CELQHROD  +00000266
    CEEOSIGG  +00000000
    CELQHROD  +00000266
    CSQBDspiOPEN+00000834 CSQBLB56 ***Exception
    Java_com_ibm_mq_jmqi_local_internal_base_Native_spiOpen
    RUNJAVATHREAD
    ...
    Java stack:
    at com/ibm/mq/jmqi/local/internal/base/Native.spiOpen(Native
    Method)
    at com/ibm/mq/jmqi/local/LocalMQ.spiOpen(Bytecode
    PC:762(Compiled Code))
    at
    com/ibm/msg/client/wmq/internal/WMQConsumerShadow.initialize(Byt
    ecode PC:1732(Compiled Code))
    at
    com/ibm/msg/client/wmq/internal/WMQSyncConsumerShadow.initialize
    (Bytecode PC:15(Compiled Code))
    *
    Additional keywords:
    ACECHNA loop
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
    *                 Release 1 Modification 0 and Release 2       *
    *                 Modification 0.                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: Inadequate serialisation between RRS    *
    *                      tasks can result in an ABEND0C4 in      *
    *                      CSQ3RRSM. The timing window which       *
    *                      results in this problem may be          *
    *                      accompanied by applications receiving   *
    *                      MQRC_LOCAL_UOW_CONFLICT and             *
    *                      MQRC_GLOBAL_UOW_CONFLICT.               *
    ****************************************************************
    CSQ3RRSM is invoked as part of RRS exit processing, and a timing
    window exists whereby the ACEATEB field is cleared while the ACE
    is still in-use. Consequently, attempts to set fields chained
    from it will cause an S0C4 abend.
    

Problem conclusion

  • The serialisation of RRS exit processing has been improved to
    prevent ACEAETB being cleared while the ACE is still in use.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PH26279

  • Reported component name

    IBM MQ Z/OS V9

  • Reported component ID

    5655MQ900

  • Reported release

    100

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2020-06-09

  • Closed date

    2020-11-09

  • Last modified date

    2021-01-04

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

    UI72460 UI72461

Modules/Macros

  • CSQ3RRSM CSQMCPRH
    

Fix information

  • Fixed component name

    IBM MQ Z/OS V9

  • Fixed component ID

    5655MQ900

Applicable component levels

  • R100 PSY UI72794

       UP20/12/08 P F012 ¢

  • R200 PSY UI72795

       UP20/12/08 P F012 ¢

Fix is available

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Document Information

Modified date:
05 January 2021