IBM Support

IT38623: Receiver channel with PipeLineLength=2 might remain in stopping status indefinitely

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APAR status

  • Closed as program error.

Error description

  • If a receiver channel is running with PipeLineLength=2, and is
    stopped either by an administrator or an Adopt MCA operation
    from a new channel instance, the channel might become stuck in
    "stopping" status indefinitely.
    
    If the stop channel was issued automatically as part of an Adopt
    MCA operation, and the configured AdoptNewMCATimeout interval
    expires, the attempt to adopt fails with AMQ9514E (channel in
    use) written to the RCVR sides error log. The corresponding
    sender channel reports AMQ9558E (remote channel unavailable) in
    its queue manager's error log.
    
    If this scenario is encountered, the channel will remain in
    stopping status will remain while its underlying TCP connection
    connected, and will be resolved if this TCP connection is
    closed, for example if terminated by a firewall, or by MQ HBINT
    logic.
    

Local fix

  • The issue can be mitigated by preventing TCP connections from
    running indefinitely, for example by setting the MQ channel
    HBINT to a value greater than 0.
    
    
    If such configuration is not possible, remove PipeLineLength=2
    from qm.ini to revert to its default value of 1.
    
    Alternatively, set/export the environment variable
    MQPIPELINELENGTH=1 in the environment used to start the queue
    manager.
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    Users of receiver channels with PipeLineLength=2 set.
    
    
    Platforms affected:
    MultiPlatform
    
    ****************************************************************
    PROBLEM DESCRIPTION:
    When PipeLineLength=2 is set, a compatible channel's workload is
    managed across two threads instead of one.
    
    A timing window existed when stopping a receiver channel running
    in this mode whereby the channel process job monitor could
    notify one of the channel's threads while it was waiting for a
    lock being held by the other thread. If the other thread did not
    yield the lock (for example, if in an indefinite socket read),
    the request would not be processed by the waiting thread and the
    channel would not stop.
    

Problem conclusion

  • The queue manager's channel job monitor logic has been modified
    so that if the channel being stopped is a RCVR channel with
    PipeLineLength=2, both threads are notified of the channel stop
    request to avoid this timing window.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v9.x CD    9.2.5
    
    The latest available maintenance can be obtained from
    'WebSphere MQ Recommended Fixes'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
    
    If the maintenance level is not yet available information on
    its planned availability can be found in 'WebSphere MQ
    Planned Maintenance Release Dates'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
    ---------------------------------------------------------------
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT38623

  • Reported component name

    MQ BASE V9.2

  • Reported component ID

    5724H7281

  • Reported release

    922

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2021-10-06

  • Closed date

    2022-01-11

  • Last modified date

    2022-01-13

  • 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

    MQ BASE V9.2

  • Fixed component ID

    5724H7281

Applicable component levels

[{"Line of Business":{"code":"LOB45","label":"Automation"},"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"922"}]

Document Information

Modified date:
14 January 2022