IT21652: MQ FOR NSS: MEMORY LEAK BECAUSE OF ERROR 2042 (OBJECT IN USE)

WebSphere MQ for HP NonStop Server V5.3.1 fix pack 5.3.1.14

APAR status

• Closed as program error.

Error description

• Memory leak because of error 2042 (object in use).
  This scenario can be reproduced with two processes:
    The first one opens a queue exclusively
  (MQOO_INPUT_EXCLUSIVE).
    It doesn't close the queue till the end of the test.
    The second one tries to open the same queue shared
  (MQOO_INPUT_SHARED)
    It fails with error 2042 and retries the open in a loop.
    The LQMA heap grows constantly.
  The application has no chance to free the Queuehandle.
  MQ returns an error code and an invalid Queuehandle.
  MQ has to deallocate the Queuehandle if this error occurs.
  

Local fix

Problem summary

•  Root cause is an incomplete error handling for
  a specific queue open error. If the application tries to open a
  queue in shared mode and the queue is already open in exclusive
  mode, the MQ-Agent replies MQRC_OBJECT_IN_USE (2042) and the
  application receives an invalid queue handle. The agent has
  already created a queue handle at this point but does not
  deallocate this handle in such a scenario.
  

Problem conclusion

•  The error handling has been extended as such
  that if error 2042 is raised, the agent process now deallocates
  the prepared queue handle.
  

Temporary fix

•  Define a very low value for the 'MaxAgentUse'
  stanza parameter in the queue maanger's qmproc.ini file. If the
  use count limit is reached, the agent process is stopped and
  will be replaced if another agent process is needed. While this
  doesn't prevent the memory leak itself, it will reduce the
  impact since the affected processes will terminate sooner.
  

Comments

APAR Information

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

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

Fix information

• Fixed component name

  WEBS MQ NSS ITA

• Fixed component ID

  5724A3902

Applicable component levels