PI65486: Z/OS MQ V8, CUSTOMER SAW AN INCREASE OF CPU CONSUMPTION WHEN USING A SHARED QUEUE USING MQGMO_SET_SIGNAL

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The customer saw an increase of CPU consumption
  when using a shared queue.  They applied the
  service parm for PM99242, which had no effect as the
  getters were using MQGMO_SET_SIGNAL rather than
  MQGMO_WAIT, and the function provided by PM99242
  only caters  for getters using MQGMO_WAIT.
  
  
  Additional Symptom(s) Search Keyword(s):
  performance
  

Local fix

• Note you need activate both PM99242 and AN6O864
  with a SERVICE parm.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 8 *
  *                 Release 0 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: High number of failed MQGET requests    *
  *                      are seen in accounting class 3 SMF 116  *
  *                      records when multiple getters are       *
  *                      waiting for messages on a shared queue. *
  *                                                              *
  *                      The getters are using MQGMO_SET_SIGNAL  *
  *                      or they are client applications using   *
  *                      SHARECNV>0 SVRCONN channels that the    *
  *                      CHIN uses MQGMO_SET_SIGNAL internally.  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When 1 or more messages arrive on a shared queue all handles
  waiting for a message on that queue are posted by the list
  transition exits. If there are more handles than messages on the
  queue, some of the handles will not find a message and will
  reenter a getwait state.
  In certain environments it is possible to post a subset of the
  handles, reducing the number of additional get requests that are
  unable to successfully get a message.
  

Problem conclusion

• When a service parameter is enabled, it will cause list
  transition processing to estimate the number of messages on a
  shared queue and post a smaller subset of handles to get those
  messages. This service parameter will now consider handles using
  MQGMO_SET_SIGNAL when determining whether a subset can be
  posted.
  
  The service parameter is not appropriate in all environments,
  and should only be enabled under direction of IBM support.
  000Y
  CSQMLTR0
  

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:

  PI66242 UI39625

Modules/Macros

• CSQMLTR0
  

Fix information

• Fixed component name

  WMQ Z/OS 8

• Fixed component ID

  5655W9700

Applicable component levels

• R000 PSY UI39625

     UP16/08/25 P F608

Fix is available

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