PI74146: MQ 8.0 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 WebSphere MQ for z/OS Version 8 *
  *                 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 V8 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.
  000Y
  CSQIMGE5
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  PI81299 UI47357

Modules/Macros

• CSQIMGE5
  

Fix information

• Fixed component name

  WMQ Z/OS 8

• Fixed component ID

  5655W9700

Applicable component levels

• R000 PSY UI47357

     UP17/07/25 P F707 ¢

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.