PI54598: WMQ Z/OS V800: PREVENT THE MESSAGES FROM BEING GENERATED OUT-OF-ORDER FOR QUEUE SERVICE INTERVAL EVENT

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Customer complains incorrect sequence of Queue Service Interval
  event message. Customer expects a "high" event should precede an
  "ok" event.
  The Queue Service Interval feature, any time the OK event is
  active,the HIGH event should be disabled and any time the HIGH
  event is active, the OK event should be disabled. So the system
  should always issue events that alternate between the two
  states - instead of two "Ok" events or two "High" events in
  a row.
  It's conceivable that while  the queue object latch is released
  before the event is actually generated.  This means that if,
  say, the putter was dispatched out by MVS just after releasing
  the latch, but before completing the HIGH event
  message generation process, there's an opportunity for the
  getting application to get dispatched in, complete an MQGET in
  a shorter time than the Service Interval, and generate an OK
  event message before the putter had been dispatched back in.
  
  This APAR is used to prevent the messages from being
  generated out-of-order based on above theory.
  

Local fix

• n/a.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 8 *
  *                 Release 0 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Queue service interval event            *
  *                      messages may be put to the              *
  *                      SYSTEM.ADMIN.PERFM.EVENT in             *
  *                      a different order than expected.        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When MQ detects that a queue service interval HIGH or OK event
  message needs to be put the event queue, the MQPUT operation is
  performed without considering the sequencing between parallel
  tasks generating event messages.
  
  This means that in situations where two or more event messages
  are generated in quick succession, it's possible that z/OS task
  dispatching may allow the second or subsequent threads to
  complete their MQPUT before the first thread.
  
  By putting the messages in an unexpected order queue monitoring
  tools that examine the most recent message put to an event queue
  may misinterpret the queue service interval state of the queue.
  

Problem conclusion

• Event message processing has been amended to ensure there is
  serialization between tasks when putting event messages to the
  queue.
  000Y
  CSQMERST
  CSQMESTP
  CSQMIAGM
  CSQMIAPE
  CSQMIAPM
  CSQMLEPL
  CSQMSTRT
  CSQM212M
  CSQXACNO
  HMS8000J
  

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:

  UI37530

Modules/Macros

• CSQMERST CSQMESTP CSQMIAGM CSQMIAPE CSQMIAPM
  CSQMLEPL CSQMSTRT CSQM212M CSQXACNO HMS8000J
  

Fix information

• Fixed component name

  WMQ Z/OS 8

• Fixed component ID

  5655W9700

Applicable component levels

• R000 PSY UI37530

     UP16/05/26 P F605

Fix is available

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