IBM Support

IT36110: Many PCF status messages flow through the channels of a Uniform Cluster even though no reconnectable applications are present

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APAR status

  • Closed as program error.

Error description

  • When using a uniform cluster, a  large number of status messages
    are being sent through cluster channels although no
    re-connectable clients are present.
    These are internal MQPCF status messages which bounce between
    queue managers as a result of them believing that their system
    topics, are no longer a local TOPICHOST.
    The problem can also impact the ability for applications to be
    re-balanced correctly
    Use runmqsc to display the topic status and check the CLROUTE
    and PUBCOUNT

Local fix

Problem summary

  • ****************************************************************
    Users of Uniform Cluster configurations.
    Platforms affected:
    When a queue manager starts, it will restore locally defined
    topic objects to the topic tree.
    After the topic tree has been initialized with defined topics,
    it can be updated with entries from the cluster cache. During
    cache restoration, updates to in the topic tree are made but
    this should not include topics which had previously been marked
    as 'DELETED' as this can modify the internal flags for topics
    which are defined locally.
    If the topic being updated is defined with CLROUTE(TOPICHOST)
    set, the internal flags were incorrectly updated, removing the
    local flag. Messages published to the TOPICSTR of the topic,
    would attempt to find an alternative TOPICHOST elsewhere in the
    cluster configuration, excluding the locally defined topic.
    If all TOPICHOST's (for a given topic string) were in this
    confused state, messages would continually flow from one queue
    manager to another attempting to find a suitable host which was
    considered to be locally defined. This appeared as though a vast
    quantity of messages are flowing through the cluster.
    With respect to Uniform Clusters, there are system topics which
    are defined with CLROUTE(TOPICHOST) that can cause the issue
    when they are deleted from the cluster.
    These topics can be marked as deleted from the cluster as a
    result of
     - issuing REFRESH CLUSTER(<uniform cluster name>)
     - removing the queue manager from the Uniform Cluster (and
    subsequently re-introducing back into the cluster)

Problem conclusion

  • The problem is resolved by preventing deleted topics from
    updating the topic tree during cache restore operations.
    The restore operations can result from :
    &#09;- After restarting the Queue Manager.
    &#09;- After enabling the SYSTEM.CLUSTER.COMMAND.QUEUE for MQGET
    The fix is targeted for delivery in the following PTFs:
    Version    Maintenance Level
    v9.1 LTS
    v9.2 LTS
    v9.x CD    9.2.4
    The latest available maintenance can be obtained from
    'WebSphere MQ Recommended Fixes'
    If the maintenance level is not yet available information on
    its planned availability can be found in 'WebSphere MQ
    Planned Maintenance Release Dates'

Temporary fix


APAR Information

  • APAR number


  • Reported component name

    MQ BASE V9.2

  • Reported component ID


  • Reported release


  • Status


  • PE




  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date


  • Closed date


  • Last modified date


  • 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


Applicable component levels

[{"Line of Business":{"code":"LOB45","label":"Automation"},"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"920"}]

Document Information

Modified date:
11 August 2021