PM78129: DUMP TITLE=CSQ1,ABN=0C4-00000011,U=SYSOPR ,C=R3600.710.CFM -CSQERCAT,M=CSQGFRCV,LOC=CSQELPLM.CSQERCAT+00000890

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The customer is running WebSphere MQ V7.1 in a 5-way QSG
  when receive:
  .
  CSQV086E +CSQ1 QUEUE MANAGER ABNORMAL TERMINATION
                 REASON=00E50702
  IEA794I SVC DUMP HAS CAPTURED:
  DUMPID=018 REQUESTED BY JOB (CSQ1MSTR)
  DUMP TITLE=CSQ1,ABN=0C4-00000011,U=SYSOPR  ,C=R3600.710.CFM
          -CSQERCAT,M=CSQGFRCV,LOC=CSQELPLM.CSQERCAT+00000890
  IEF450I CSQ1MSTR CSQ1MSTR - ABEND=S6C6 U0000 REASON=00E50702
  .
  The change team has taken a look at the dump for the 0C4 in
  CSQERCAT. It is due to an error in the handling of the IVSA
  object used in a request to refresh the local representation
  of a shared queue after an update.
  .
  An alter was made to queue SHR_QUEUE significant enough to
  trigger messages to all QMGRs in the QSG to request them to
  update their local representation of the queue.
  To do this update, CSQMELTRX calls CSQMLTRX, which schedules
  an asynchronous request to CSQMLTR0 to do the update. CSQMLTR0
  calls CSQMREF1 to do the processing. CSQMREF1 is getting the
  IVSA latch for the queue, and as it is held, is suspended for
  2 seconds in this case.
  .
  While being suspended, the queue is deleted on CSQ8, causing
  the IVSA on CSQ9 to be released. By the time CSQMREF1 is
  resumed (after obtaining the latch), the IVSA has been
  reallocated to a local queue. This causes some unexpected data
  in some of the IVSA fields. When using it, the 0C4 abend
  occurs.
  .
  The root cause seems to be missing synchronisation, allowing
  the queue to be deleted whilst we are attempting to update its
  local representation.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of Websphere MQ for z/OS Version 7 *
  *                 Release 1 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Alteration and subsequent deletion of a *
  *                      shared queue, and new queues being      *
  *                      defined on another queue manager in the *
  *                      same queue sharing group may cause a    *
  *                      0C4 abend with reason 00000011.         *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When a shared queue is being altered by one queue manager in a
  QSG, a request will be propagated throughout the QSG instructing
  other queue managers to update their local representation of the
  shared queue object.
  
  While this process is ongoing, if another member of the QSG
  happens to delete the same shared queue there is a timing window
  where the IVSA control block representing the original queue may
  be deleted and even reused by another queue. When the request to
  propagate the original alter command completes, the queue
  manager may still be using the IVSA that has been removed and
  subsequently reallocated. This leads to the S0C4 abend occurring
  when attempting to use the now-incorrect IVSA block.
  

Problem conclusion

• The alter processing has been amended to flag the local
  representation of the queue for the duration of the operation.
  This flag restricts the ability to delete the local queue
  representation while on. This ensures the object is
  still valid for the entire duration of the processing.
  100Y
  CSQELTRX
  CSQICDSQ
  CSQMLTR0
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  UK91135

Modules/Macros

• CSQELTRX CSQICDSQ CSQMLTR0
  

Fix information

• Fixed component name

  WMQ Z/OS V7

• Fixed component ID

  5655R3600

Applicable component levels

• R100 PSY UK91135

     UP13/03/01 P F302 Ž

Fix is available

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