PK36223: CICS MQ DB2 BACKOUT IS INCORRECT AFTER A TRANSACTION ABEND IN A MULTI-CICS ENVIRONMENT. CICS IS THE COORDINATOR

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• When in a multi region environment using DPL to move request
  from a QOR to an AOR, that is updating DB2 tables, a problem can
  occur if the transaction running in the AOR ABENDs.
  CICS is designated as the coordinator in the 2 phase commit, the
  request from MQ (QOR region) commits forward, but the changes
  made in DB2 and CICS are backed out.
  ADDITIONAL KEYWORDS:  two-phase AD2R ABENDAD2R syncpoint mirror
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS user accessing DB2 resources.       *
  ****************************************************************
  * PROBLEM DESCRIPTION: SYNCPOINT processing, after a handled   *
  *                      FORCEPURGE of a task within the DB2     *
  *                      interface, may lead to the inconsistent *
  *                      updating of resources.                  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A task updates a variety of CICS and external resources ( for
  example MQ ). For each resource updated its controlling manager
  will register an interest so it can take part in SYNCPOINT
  processing.
  
  A HANDLE-ABEND condition is active.
  
  The task then issues an SQL call which causes the DB2 Resource
  Manager Interface to be invoked. The request is passed to DB2
  for execution. By this point the transaction is now running
  under an OTE(L8) TCB.
  
  Upon receipt of the request DB2 determines that the target
  resource ( DB2 Table ) is in use so places the caller in an
  internal wait. Due to other factors the target table remains
  unavailable for some time.
  
  At some point it is decided that the task is to be terminated,
  by user intervention, due to its lack of response. This is
  accomplished by the use of CEMT S TAS() FORCEPURGE, the action
  of which is to abend the L8 TCB waiting within DB2. DB2, via EOT
  broadcast, detects this abend and performs rollback recovery on
  any of its resource that have been altered by previous DB2
  requests from this task.
  
  In parallel to the steps taken by DB2, CICS also takes steps to
  recover from the force purging of the task. This involves
  releasing controls blocks used in the management of the task's
  connection to DB2. It also removes the DB2 Resource manager's
  interest in SYNCPOINT processing for this task.
  
  Control returns to the application with and abend code AD2R.
  This abend code is HANDLED and application processing continues
  by issuing a EIP SYNCPOINT call. All interested resource
  managers are called to take part in commit processing, except
  DB2 as it reset its interest due to the earlier abend. As DB2
  takes no part it cannot vote NO to commit so the call is
  successful, meaning DB2 resources have not been updated where
  others have been committed.
  

Problem conclusion

• The task abend processing in CICS module DFHD2EX1 has been
  amended. It will still release the Connection control block but
  it will now retain the DB2 Resource Managers interest in
  SYNCPOINT processing for the task. The lack of a connection
  control block will cause SYNCPOINT requests to fail with a
  "LOST_OUR_THREAD" abend but this will lead to the DB2 Resource
  Manager voting against the committing of any updates.
  

Temporary fix

• FIX AVAILABLE BY PTF ONLY
  

Comments

APAR Information

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

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

  UK23860

Modules/Macros

•    DESD2EX1 DFHD2EX1
  

Fix information

• Fixed component name

  CICSTS 3.1 Z/OS

• Fixed component ID

  5655M1500

Applicable component levels

• R400 PSY UK23860

     UP07/04/12 P F704

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.