PH23608: MQ CHIN ABEND 0C4-00000010 ABN= 0C4- 00000010,C=MQ900.910.CHIN,M=CSQXDISP,LOC=CSQXRCTL.CSQXCCMX+00432

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• When a multiplexed channel that has the socket drop underneath
  it there is a path in the code that allows for some storage to
  be used after it has been freed and reused by another process,
  thus allowing the 0C4 to occur. One of the indications that
  this path has been followed is the appearance of the CSQX772E
  message with MQRC=2202 (MQRC_CONNECTION_QUIESCING) in the
  channel initiator job logs.
  .
  Additional symptoms that might occur after the ABEND0C4 in
  CSQXCCMX:
  - ABN= 5C6-00E70054,C=MQ900.910.CHIN
    ,LOC=CSQXADPM.CSQXADPM+07200
  - At shutdown of the CHIN:
    ABN= 5C6-00E70004,C=MQ900.910.CHIN
    ,LOC=CSQXSUPR.CSQXSCHD+004CC
  - Hang of CHIN during shutdown.
    CHIN trace shows loop at:
    CSQACRTT Create data conv tables
  

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: Abend 0C4 in CSQXCCMX occurs following  *
  *                      a network error on a client connection  *
  *                      with SHARECNV > 0                       *
  ****************************************************************
  While sending a message to the client, the asynchronous
  consumer thread encountered a network error. The next time the
  receive thread queued a request to the consumer thread, the
  response was updated to indicate the error. However this also
  led to an inconsistent view of the consumer state.
  During termination of the channel, this opened a timing window
  where the consumer thread could attempt to access storage that
  had already been freed by the receive thread.
  

Problem conclusion

• The serialisation between the receive thread and the consumer
  thread is updated to prevent the inconsistent view of the
  consumer state, and consequently to ensure that the receive
  thread does not free the affected storage until it is no longer
  required by the consumer thread.
  

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:

  UI71007 UI72437

Modules/Macros

• CSQXCCAX CSQXRSTM
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R100 PSY UI71007

     UP20/11/02 P F010

• R200 PSY UI72437

     UP20/12/07 P F012

Fix is available

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