PM76990: ABEND502 CSQXDISP DUE TO SPACE RUNNING OUT IN THE EVENTS TABLE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• ABEND502 in load module CSQXDISP occurs as space looks to have
  run out in the z/OS events table for the async consumer
  notification TCB (ACNO). The ACNO task has been dispatched
  but is being suspended. If the ACNO task gets busy, the
  overhead from its storage requests (which are done via MVS
  STORAGE/OBTAIN release) can cause its TCB to be suspended while
  waiting on the local lock. During this time ECB events for
  notification of message arrivals continue to be posted. In
  this APAR's case it appears that the number of post events
  has exceeded the ACNO's EVENTS table capacity due to the
  overhead of the additional STORAGE requests. This results
  in the EVENTS table reaching its maximum capacity and POST
  failing with ABEND502.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere MQ for z/OS           *
  *                 Version 7 Release 0 Modification 1 and       *
  *                 Release 1 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Abend S502 may occur when a large       *
  *                      number of messages arrive for           *
  *                      waiting SVRCONNs at once.               *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When a very large number of messages arrive for waiting SVRCONN
  channels with a non-zero SHARECNV value, it is possible under
  certain circumstances that the processing of the arrival
  notifications for these messages may result in the events table
  filling up for the async-consumer notification task.
  
  This occurs because the task is performing diagnostic tracing
  that requires a small amount of automatic storage to be obtained
  and released for every message that arrives.
  
  Because of this overhead, the processing is slowed down and in
  rare circumstances it is possible for the events table to fill
  up resulting in an S502 abend.
  

Problem conclusion

• The processing of the async-consumer notification task is
  amended so that no storage needs to be obtained when tracing.
  
  In addition, the dispatch priority of the TCB has been raised
  and the size of the z/OS events table for the ECBs has been
  increased.
  010Y
  100Y
  CSQXACNO
  CSQXJST
  CSQXSFRE
  CSQXSGET
  

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:

  UK83814 UK83815

Modules/Macros

• CSQXACNO CSQXJST  CSQXSFRE CSQXSGET
  

Fix information

• Fixed component name

  WMQ Z/OS V7

• Fixed component ID

  5655R3600

Applicable component levels

• R010 PSY UK83814

     UP13/01/16 P F301

• R100 PSY UK83815

     UP13/01/16 P F301

Fix is available

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