PH61863: ABEND5C6 00E70054

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• This ABEND5C6 can occur due to a consumer registered on a
  handle persisting beyond the life of the channel that
  established it. When a message arrives on the associated queue,
  an attempt is made to process it to via a new channel that has
  been allocated the same EB, however this attempts to use values
  from freed/reused storage. In the APAR'd case the freed storage
  remained accessible while the initial validity checks were
  made, but was reused prior to the failing MQCB call, resulting
  an invalid conv address being passed.
  
  Depending on the timing of storage reuse, it is likely that the
  other abends reported ( ABEND0C4 in CSQXXGTE ), which is also
  due to an unexpected conv address being passed elsewhere in
  processing, are also symptoms of the same underlying error.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 3 Modification 0 and                 *
  *                 Release 4 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Various errors can occur when a channel *
  *                      establishes a message consumer on an EB *
  *                      previous used for an XA connection.     *
  *                      Symptoms can include:                   *
  *                      - Abend 0C4 in CSQXXGTE                 *
  *                      - 5C6-00E70054 in CSQXADPM              *
  *                      - CSQX053E "CSQXFFST Error information  *
  *                        recorded in CSQSNAP data set", with   *
  *                        an associated FFST record from        *
  *                        rstConsumer                           *
  *                      - IPPROCS > 0 for a queue previously    *
  *                        accessed by an XA channel             *
  *                      - Messages consumed from a queue        *
  *                        previously used by an XA channel      *
  ****************************************************************
  During processing of an xa_close request, CSQMCPRH queues the
  EB used by the channel on the MCLB free chain for reuse, however
  it does not close any queues that were still open for the
  svrconn channel until a subsequent end thread request.
  A timing window exists where the EB can be reused by a different
  channel, causing the queue handles to remain open for the new
  channel.
  If the new channel is a svrconn channel with SHARECNV 1 or above
  it is possible that the channel will attempt to consume messages
  from those handles, leading to unpredictable behaviour,
  including the reported symptoms.
  

Problem conclusion

• CSQMCPRH will close any open handles when processing an xa_close
  request prior to allowing the EB to be reused.
  

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:

  UI99423 UI99424

Modules/Macros

• CSQMCPRH
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R300 PSY UI99424

     UP25/01/07 P F501 ¢

• R400 PSY UI99423

     UP25/01/07 P F501 ¢

Fix is available

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