PI87591: MQ: ABEND5C6-00940001 occurs in CSQMCPRH for an IMS job

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• *CSQV086E +CSQ1 QUEUE MANAGER ABNORMAL TERMINATION
  REASON=00940001
   IEA794I SVC DUMP HAS CAPTURED:
   DUMPID=nnn REQUESTED BY JOB (xxxxxxxx)
   DUMP TITLE=CSQ1,ABN=5C6-00940001,U=uuuuuuuu,C=MQ900.900.CMC -CS
              QMCPRH,M=CSQGFRCV,LOC=CSQMCGLM.CSQMCPRH+000032B8
   IEF450I CSQ1MSTR CSQ1MSTR - ABEND=S6C6 U0000 REASON=00940001
  
  An IMS connection was processing a close_all_handles request
  (part of disconnect processing). The abend occurred because at
  completion of this call MQ detects that an internal latch
  remains held. This is an unexpected situation as the latches
  are a short-term serialization mechanism which should not be
  retained across API calls.
  
  There is a timing window where one MQ task can delete a control
  block which still needs to be referenced by an IMS task. If the
  deletion occurs, then it is possible for the control block to
  be allocated to another task and the fields updated before the
  IMS task is able to finish using it. This can result in the
  latch-held flag being left on for the IMS task. The point in
  the code where this could occur is only a few instructions
  long, so it would be rare for the two tasks to be processing in
  a way which would cause the issue.
  
  Additional Symptom(s) Search Keyword(s):
  ABENDS5C6 S5C6 S05C6 00940001
  

Local fix

• A ++APAR is available from the support center.
  .
  Another option is to turn off SMF 116 CLASS(3) data.  Be aware
  this controls thread and queue level accounting information.
  Consider carefully your use of the data before deciding whether
  to turn it off using the MQ command:
    STOP TRACE(ACCTG) DEST(SMF) CLASS(03)
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 0 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Abend S5C6-00940001 occurs in CSQMCPRH  *
  *                      when an IMS BMP or transaction ends,    *
  *                      and class 3 accounting is turned on.    *
  *                      The abend is followed by abnormal       *
  *                      queue manager termination 6C6 with      *
  *                      REASON=00940001                         *
  ****************************************************************
  CSQ7COLL was called for a close_all_handles request to collect
  accounting information for the terminating IMS transaction.
  After collecting the information, the WQELI for the transaction
  was added to the chain of WQELI's for deallocation processing,
  and the WQELI latch was released.
  However, between the WQELI being added to the chain, and the
  latch being released CSQ7PLRT was resumed by another task and
  processed the deallocation chain, leading to the WQELI being
  freed.
  When the latch release took place, the WQELI had been reused,
  and so it appeared that the latch was not held. However the EB
  for the task still indicated a latch was held.
  When CSQMCPRH later checked for unreleased latches, it detected
  that the EB still held a latch - this is unexpected, and led
  to the reported abend and queue manager termination.
  

Problem conclusion

• CSQ7COLL is changed to release the latch prior to chaining the
  WQELI on to the deallocation chain.
  

Temporary fix

Comments

APAR Information

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

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

  UI51299

Modules/Macros

• CSQ7COLL CSQ7PLRT
  

Fix information

• Fixed component name

  MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R000 PSY UI51299

     UP17/11/21 P F711 ¢

Fix is available

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