IT34822: A non-persistent message may be discarded if a waiting async MQGET times out while an MQPUT is delivering to it

APAR status

• Closed as program error.

Error description

• A non-persistent message is not present on a queue after the
  MQPUT (outside of syncpoint) completes, but it was not received
  by any MQGET caller.
  
  Analysis of the diagnostics from the queue manager shows that
  the message was in the process of being delivered to a waiting
  MQGET call from an asynchronous consumer (also outside of
  syncpoint), however the MQGET timed out before the message was
  delivered successfully, but the message was not added to the
  queue.
  

Local fix

• Use synchronous MQGET API calls, or consume messages from the
  queue under an MQ syncpoint.
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  User applications performing Async Consume operations where the
  messages are non persistent
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  When an application is putting a message, the queue manager may
  determine that there is a getting application (in this instance
  an asynchronous consumer) waiting to receive messages which it
  can give the message to directly. There is a timing window
  whereby the consumer has completed its wait interval just as the
  queue manager is getting ready to hand the message over to it
  (avoiding the the queue)
  
  Synchronous MQGET processing accounts for this scenario when it
  completes its wait interval and perform additional processing to
  receive the message from queue manager by waiting until the put
  processing has completed if necessary. However, a logic error
  meant that asynchronous consumer processing failed to correctly
  check for this scenario and returned MQRC_NO_MSG_AVAILABLE
  (2033) to the consumer application.
  
  At this point, because the message was not going to be placed on
  a queue by MQPUT processing (and because the message was non
  persistent) the message is then lost.
  

Problem conclusion

• The problem is resolved with the inclusion of code present for
  normal MQGET processing for the specific timing related
  scenario.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v8.0       8.0.0.16
  v9.0 LTS   9.0.0.12
  v9.1 LTS   9.1.0.8
  v9.2 LTS   9.2.0.2
  v9.x CD    9.2.2
  
  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:

  IT37229

Fix information

• Fixed component name

  IBM MQ BASE MP

• Fixed component ID

  5724H7271

Applicable component levels