IT42126: Channel intermittently enters Initializing/Retrying loop and will not restart

APAR status

• Closed as program error.

Error description

• Using IBM MQ 9.1, a channel remains stuck in an
  initializing/retrying state.  The messages on the transmit queue
  increase as they are not able to be sent to the destination
  queue manager.  Sometimes, "AMQ9514: Channel in Use" is reported
  for the channel in the queue manager error log, even though the
  channel is not running
  

Local fix

• Sometimes, recycling of the qmgr works.
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue has been occasionally seen on MQ 9.1 sender/receiver
  channels, including cluster channels.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  A small timing window meant that an internal status record might
  not be correctly updated during the termination of a channel
  thread. This then caused the queue manager to incorrectly
  determine the old channel instance was still running when a new
  instance of the channel attempted to start.
  

Problem conclusion

• Code to scan the channel status table is altered so that the
  status reflects properly when a channel goes out of scope. This
  additional check incurs a slight performance hit and so due to
  the very small number of observations of this issue in customer
  deployments, an environment variable must be set to enable these
  additional status checks:
  
  AMQ_CHL_PIDTID_CHECK=1
  
  Design changes to the channel status logic in newer version of
  MQ mean that they are not susceptible to this timing window.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.1 LTS   9.1.0.20
  
  The latest available maintenance can be obtained from
  'IBM MQ Recommended Fixes'
  https://www.ibm.com/support/pages/recommended-fixes-ibm-mq
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'IBM MQ
  Planned Maintenance Release Dates'
  https://ibm.biz/mqplannedmaintenance
  
  ---------------------------------------------------------------
  

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

  IBM MQ BASE MP

• Fixed component ID

  5724H7271

Applicable component levels