IT16182: Slow performance of BROWSE_NEXT on deep queue after a message isremoved

APAR status

• Closed as program error.

Error description

• An application removes a message that is under a browse cursor
  that is being kept for the same HObj or another HObj.  That HObj
  is then used in a call to MQGET with MQGMO_BROWSE_NEXT.  The
  MQGET takes a long time to return, if the queue is deep.
  
  If the return from MQGET is 2033 MQRC_NO_MSG_AVAILABLE then the
  next MQGET is also slow.
  
  This is most visible if the queue is deep, and the message that
  was removed is near the end of that queue.
  
  Trace shows that MQ iterates through each message on the queue
  every time a queue BROWSE_NEXT is called.
  
  This issue can be created by browsing the last message on
  the queue, consuming it, and then continuing to browse. Each
  browse will iterate through every message on the queue until
  we hit the end of the queue and return 2033.
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  Users who concurrently browse and consume MQ messages using the
  same HObj (object handle) or a different HObj.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  The problem was caused by a combination of internal flags that
  is set when a message is destructively consumed. These flags
  caused IBM MQ to iterate through every message on the queue each
  time that MQGET is called with MQGMO_BROWSE_NEXT.
  

Problem conclusion

• A new internal flag has been introduced which will allow IBM MQ
  to continue browsing from the point in the browse list where a
  message was last destructively consumed.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v7.1       7.1.0.9
  v7.5       7.5.0.8
  v8.0       8.0.0.5
  
  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 is sysrouted FROM one or more of the following:

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

Fix information

• Fixed component name

  WMQ BASE MULTIP

• Fixed component ID

  5724H7241

Applicable component levels