PH70922: ABEND0C4 00000011 IN CSQXCCMX OFFSET 00418

APAR status

• Closed as program error.

Error description

• User reports SVRCONN connections end abnormally as an ABEND0C4
  within CSQXCCMX is generated. Related CSQSNAP output is
  collected. This is out of function ccxFreeMem as it detects an
  unexpected condition. Development finds that the abend in
  CSQXCCMX and FFST for XFFSccxFreeMem are due to contents not
  being found in the cache.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 4 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: An 0C4 abend occurs in CSQXCCMX when an *
  *                      asynchronous consumer connection closes *
  *                      while message processing is still in    *
  *                      progress. It is also possible to see    *
  *                      FFSTs in ccxFreeMem stating "Memory not *
  *                      in cache" or "invalid handle".          *
  ****************************************************************
  A timing window exists where the thread performing the async
  send can be suspended during network I/O while transmitting a
  message back to the client. If another thread tears down this
  connection during this suspension, a structure related to the
  async send is freed. When the async thread resumes and attempts
  to clean up, it passes invalid memory into csqxccmx, causing an
  0C4 abend.
  

Problem conclusion

• The code has been changed so that during the async thread
  cleanup, a valid pointer is dereferenced, preventing the abend.
  

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:

  UO08318

Modules/Macros

• CMQXRSTF
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels