PI81299: MQ 900 Z/OS-HIGH CPU CONSUMPTION IN CHIN - CLIENT CHANNEL IS BROWSING MESSAGES PUT ON THE QUEUE BEFORE MQ V7

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• A client channel (running mqmonntp.exe) is browsing messages
  on a queue. The messages were put on the queue before
  MQ v7. Routine rstCheckForOneMessage in CSECT CMQXRSTF / LMOD
  CSQXRCTL was continually trying to retrieve them.
  
  The problem is that the MQGET processing keeps returning
  MQRC_TRUNCATED_MSG_FAILED with DataLength set to the
  length of the message, x561, although a large enough
  buffer has been supplied, x561.
  The problem was in CSQIMGE5 when processing a message
  put before MQ V7 (i.e. in an IRH2) which contains an
  RFH2 (len_moved is not updated with the length of the
  RFH2 put into the buffer by CSQMHDRS).
  
  The loop occurs when using a client with SHARECNV > 0 to browse
  the queue in question.
  .
  Additional Symptom(s) Search Keyword(s):
  MQMON
  MQMON session
  

Local fix

• If you want to delete the message from the queue, a couple of
  options are:
  1) CLEAR QLOCAL (this will remove all messages on the queue)
  2) Have a program, e.g. a batch job, do an MQGET for the
     MSGID of the specific message with MQGMO_ACCEPT_TRUNCATED_MSG
     (otherwise the MQGET will always fail with
     MQRC_TRUNCATED_MSG_FAILED no matter how big the buffer
     supplied).
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users of IBM MQ for z/OS Version 9 Release 0             *
  * Modification 0.                                              *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * Client application getting a message with message properties *
  * in a message handle can cause the CHIN address space to loop *
  * resulting in high CPU usage.                                 *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Messages created in pre-V7 queue managers that have remained in
  queues after migration to V9 and they have RFH2 headers can
  cause the CHIN loop when a client application gets the message
  with option MQGMO_PROPERTIES_IN_HANDLE or
  MQGMO_PROPERTIES_AS_Q_DEF and the queue has attribute
  PROPCTL(ALL).
  

Problem conclusion

• CSQIMGE5 has been updated to process pre-V7 messages with RFH2
  correctly without causing the CHIN to loop.
  

Temporary fix

Comments

APAR Information

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

  PI74146

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

  UI47358

Modules/Macros

• CSQIMGE5 none
  

Fix information

• Fixed component name

  MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels

• R000 PSY UI47358

     UP17/08/10 P F708 ¢

Fix is available

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