PH27898: MQ MEMORY LEAK IN PUBSUB TOPIC SCAVENGER ROUTINE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The original problem description from APAR IT15770 for WebSphere
  MQ and IBM MQ for multi-platforms:
  ----------------------------------------------------------------
  Available memory on the system may either become exhausted or
  may be seen to be increasing in an unbounded manner.
  
  Further investigation may show that the Java JVM process and the
  MQ amqzmuc0 process are using a large amount of memory.
  --------------------------------------------------------
  
  Symptoms for this APAR for IBM MQ for z/OS:
  ------------------------------------------
  - The leak of 64 bit storage can be observed by a continually
    decreasing amount of free "above bar" storage in the
    following message:
  
    CSQY220I CSQSCTL Queue manager storage usage:
    local storage: used nnnnMB, free nnnnMB: above bar: used nGB,
    free nnnnMB
  
  - If the above-the-bar storage for MQ (capped by MEMLIMIT) is
    exhausted, the following message will occur:
  
    CSQY227E CSQSHGMN Unable to allocate storage
    above the bar using IARV64, RC=00000008, reason=4A001620
  
  - Dumps:
  
    ABN=5C6-00A30042,U=userid,C=MQ900.900.SMC -CSQSHGMN,
    M=CSQGFRCV,LOC=CSQSLD1 .CSQSHGMN+00001140
  
    ABN=5C6-00E7014F,C=MQ900.900.CHIN,R=E7404040,
    LOC=CSQXADPM.CSQXADPM+05274
  
    In the output of
      LISTHIMO asid
      (where 'asid' is the queue manager's hexadecimal ASID)
    the 64bit MOMB blocks point to storage with TPFX eyecatchers.
    The PFX+1C points to R14 for CSQTOGMN's caller. The nearest
    eyecatcher going back is kqiTopicCreateSubscriberLink. That
    routine is in CSECT CMQXKTPU in load module CSQTOPLM.
  

Local fix

• If it is possible to increase MEMLIMIT for the MSTR job, that
  will increase the time before storage is exhausted.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 0 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Users with large number of topic nodes  *
  *                      in their topic tree may run out of      *
  *                      above the bar storage. The following    *
  *                      message may be seen:                    *
  *                      CSQY227E CSQSHGMN Unable to allocate    *
  *                      storage above the bar using IARV64,     *
  *                      RC=00000008, reason=4A001620            *
  ****************************************************************
  The topic scavenger routine, which checks and reclaims the space
  used by dynamic topic nodes, does not correctly free all
  allocated storage for nodes in the topic tree. On systems with
  a large number of topic nodes in their topic tree this can
  result in a rise in reported storage usage in message CSQY220I,
  and can lead to exhaustion of above-the-bar storage.
  

Problem conclusion

• The code has been corrected to free all storage associated with
  a topic node once it is removed from the tree.
  

Temporary fix

Comments

APAR Information

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

  IT15770

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

  UI72349

Modules/Macros

• CMQXKTPU
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R000 PSY UI72349

     UP20/12/07 P F012 ¢

Fix is available

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