PH69823: SHARED IMS BRIDGE QUEUE SHUTDOWN PROCESSING HANGS DUE TO ORPHANED QCP0 SRB

APAR status

• Closed as program error.

Error description

• When an IMS region shuts down, the queue manager may fail to
  disconnect properly from a shared IMS bridge queue. The expected
  CSQ2011I and CSQ2010I messages are missing from the queue
  manager log, and the queue manager does not reconnect when IMS
  restarts. The queue manager and IMS show inconsistent connection
  states, preventing IMS transactions from being processed.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
  *                 Release 4 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: When an IMS region shuts down, the      *
  *                      queue manager may fail to disconnect    *
  *                      properly from a shared IMS bridge       *
  *                      queue. The expected CSQ2011I and        *
  *                      CSQ2010I messages are missing from the  *
  *                      queue manager log when the IMS regions  *
  *                      disconnects and attempts to reconnect.  *
  *                      The queue manager and IMS show          *
  *                      inconsistent connection states,         *
  *                      preventing IMS transactions from being  *
  *                      processed.                              *
  ****************************************************************
  A race condition exists in the IMS bridge shutdown logic. When
  an IMS region disconnects, a timing window allows a new bridge
  queue task to be created after shutdown has begun but before the
  shutdown wait loop starts. This occurs when another queue
  manager in the queue sharing group releases a shared IMS bridge
  queue, triggering the creation of a new bridge queue task that
  never receives a shutdown signal. The queue manager waits
  indefinitely for this orphaned task to terminate, preventing
  completion of the disconnection process.
  

Problem conclusion

• The code has been corrected to set a shutdown flag when IMS
  bridge member shutdown begins. New bridge queue tasks now check
  this flag after initialization and exit immediately if shutdown
  is in progress, allowing the disconnection process to complete
  successfully.
  

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:

  UO07725

Modules/Macros

• CSQ2MEM0 CSQ2MEM1 CSQ2QCP0
  

Fix information

• Fixed component name

  IBM MQ Z/OS V9

• Fixed component ID

  5655MQ900

Applicable component levels