PM92693: WMQ Z/OS: RESOLVE CHANNEL PROCESSING FOR A CLUSTER CHANNEL HOLDS A LOCK WHICH CAN DELAY OTHER CHANNEL STARTS/STOPS.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• During  RESOLVE CHANNEL ACTION(BACKOUT) processing for a
  cluster sender channel, message reallocation processing
  (indicated by CSQX191I)  will take place. This involves
  retrieving all messages on the SYSTEM.CLUSTER.TRANSMIT.QUEUE
  which are intended to be sent by the channel being resolved, in
  order to see if they can be sent by another channel. If there
  are a large number of messages for this channel, this
  processing takes some time. While the RESOLVE CHANNEL
  processing is occurring, a lock needs to be held on the CHIN's
  channel status table, which can cause a delay in channels
  starting/stopping/retrying and can cause a temporary build-up
  of messages on SYSTEM.CHANNEL.INITQ.
  
  This APAR is being raised to investigate whether a change may
  be able to be made to limit the impact of this message
  reallocation processing on the starting/stopping of other
  channels.
  
  Additional Symptom(s) Search Keyword(s):
  starting stopping retrying stop start retry
  wait hang hung performance
  CSQX191I rrmReallocMsgs
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere MQ for z/OS version 7 *
  *                 Release 1 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Unable to stop or start any channels    *
  *                      after RESOLVE CHANNEL ACTION(BACKOUT)   *
  *                      has been issued against a cluster       *
  *                      sender channel.                         *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  When RESOLVE CHANNEL(x) ACTION(BACKOUT) is issued against a
  cluster channel rrxResolveChannel may invoke rrmReallocMsgs
  in order to find an alternative destination for any messages on
  the SYSTEM.CLUSTER.TRANSMIT.QUEUE. However if the queue
  contains many thousands of messages then rrmReallocMsgs will
  take some time to complete. During this time rrxResolveChannel
  still has a lock on the channel status table which means that it
  will be impossible for any channels to be stopped or started.
  

Problem conclusion

• rrxResolveChannel in CSQXRCMN has been changed so that it
  it will release the lock on the channel status table before
  calling rrmReallocMsgs.
  100Y
  CSQXRCMN
  

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:

  UK97824

Modules/Macros

• CSQXRCMN
  

Fix information

• Fixed component name

  WMQ Z/OS V7

• Fixed component ID

  5655R3600

Applicable component levels

• R100 PSY UK97824

     UP13/10/16 P F310

Fix is available

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