PH64489: MAXTASK SITUATION CAN HAPPEN BY TWO CFTL TASKS DEADLY EMBRACES EACH OTHER ON UMT(USER MAINTAINED DATA TABLE)

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Customer experienced transactions waiting for a file to open
  would delay and then timeout with AFCY, eventually the region
  went MXT.
  The dump will show two CFTL tasks deadly embraces each other on
  KCADDR enqueue and FCFLUMTL enqueue.
  In this situation Max task would be expected since CFTL could
  not work so transactions build up waiting for files to open.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS Users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: Two CFTL tasks can be attached to load  *
  *                      the same User Maintained Data Table     *
  *                      file. These tasks will eventually       *
  *                      deadlock with each other, leading to    *
  *                      CICS needing to be restarted.           *
  ****************************************************************
  When opening a User Maintained Data Table (UMT) file, there is a
  specific code path within interleaving tasks that can lead to
  the shared data table loading transaction (CFTL), being attached
  after the file has been opened and another task closing the
  file just before CFTL begins to browse the file. The browse
  request will find the file closed and issue an implicit open
  which will attach another CFTL transaction. Now there are two
  CFTL transactions that are going to attempt to browse and load
  the same file. This can result in a deadlock. The consequence of
  the deadlock can vary but may result in max task being reached
  and CICS needing to be restarted.
  

Problem conclusion

• DFHDTLX has been altered to ensure that if the file being
  loaded is closed prior to the beginning of the start browse,
  then the browse request is not made so no second CFTL
  transaction will be attached and no deadlock can occur.
  

Temporary fix

Comments

APAR Information

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

  PH60424

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

  UI99672 UI99673

Modules/Macros

• DFHDTLX
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UI99673

     UP25/01/18 P F501 ¢

• R500 PSY UI99672

     UP25/01/17 P F501 ¢

Fix is available

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