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

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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 number

    IT21652

  • Reported component name

    WEBS MQ NSS ITA

  • Reported component ID

    5724A3902

  • Reported release

    531

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2017-08-01

  • Closed date

    2017-08-15

  • Last modified date

    2017-08-15

  • 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

[{"Business Unit":{"code":"BU048","label":"IBM Software"},"Product":{"code":"SSCPQ5M","label":"APAR"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"5.3.1","Edition":"","Line of Business":{"code":"","label":""}}]

Document Information

Modified date:
15 August 2017