PI07566: WEBSPHERE MQ Z/OS 7.1.0:MQ BATCH DELETE PROCESSING IMPROVEMENT

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Batch delete processing can either be triggered when  the batch
  delete buffer is full (341 messages), or a put to a shared
  queue fails due to a "structure full" event.
  However, the latter is only attempted on the queue manager
  issuing the MQPUT. Thus the call can  still fail if the CF is
  full due to entries on the uncommitted list headers for other
  queue managers in the QSG.
  Exposure to this issue is increased if the queue managers doing
  the  MQGET calls are not doing any MQPUT calls to that same
  structure, as entries will build up on the uncommitted list
  header, until the batch  delete buffer is full, without any
  MQPUT calls that could trigger early batch delete processing
  due to a "structure full" event.
  Having a system with an even distribution of MQPUT and MQGET
  calls to the CF structure will reduce, though not eliminate,
  exposure to the structure full issue. The value that triggers
  normal batch delete processing can be improved,  to avoid
  waiting for a full buffer in a scenario where the structure
  could run out of space earlier.
  Using the number of queue managers in the QSG, and the size of
  the CF structure, MQ should be able to adapt the limit to
  something more appropriate.
  

Local fix

• N/A.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 7 *
  *                 Release 1 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Unexpected conditions of CF Structure   *
  *                      full and MQPUT calls to shared queues   *
  *                      on that structure failing with MQRC     *
  *                      2192 (MQRC_STORAGE_MEDIUM_FULL) due to  *
  *                      used structure space that has not been  *
  *                      released by queue managers in the QSG.  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When MQGET calls for a shared queue are issued with the
  MQGMO_NO_SYNCPOINT option, the message will be moved from the
  queue list header in the CF application structure to the
  uncommitted list header for the particular queue manager.
  The entry is not deleted immediately, but added to a list of
  entries to delete by batch at a later stage.
  Depending on the setup of the CF structure and the QSG, this can
  result in a situation where entries left on the uncommitted list
  headers fill up the structure before the batch delete is
  triggered. For instance a fairly small CF structure, with a
  larger number of queue managers in the QSG and larger messages
  on the shared queues can cause this to happen.
  

Problem conclusion

• A service parm was added to enable a calculation of the batch
  delete limit for application structures when the queue managers
  first connects to the structure, taking into account the size of
  the CF structure, as well as the number of queue managers in the
  QSG.
  Please note that will reduce the amount of storage used in the
  CF, but increase the CF CPU usage, as calls to delete entries
  from the CF structure are issued more often.
  The service parm should only be used under guidance from IBM
  support.
  100Y
  CSQEBDEL
  

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:

  UI14614

Modules/Macros

• CSQEBDEL
  

Fix information

• Fixed component name

  WMQ Z/OS V7

• Fixed component ID

  5655R3600

Applicable component levels

• R100 PSY UI14614

     UP14/03/04 P F403

Fix is available

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