PI66242: Z/OS MQ V9, 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

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users of IBM MQ for z/OS Version 9 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:                                              *
  * N/A                                                          *
  ****************************************************************
  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.
  

Temporary fix

Comments

APAR Information

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

  PI65486

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

  UI40455

Modules/Macros

• CSQMLTR0
  

Fix information

• Fixed component name

  MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R000 PSY UI40455

     UP16/11/02 P F610

Fix is available

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