PK06748: CICS LOOPS WHEN RUNNING JAVA PROGRAM, MAY SEE DFHSM0139. PROBLEM MAY OCCUR WHEN MAXJVMTCBS OR MAXXXXXTCBS VALUE REACHED.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• CICS goes into a loop when running a JAVA program.  You may see
  message "DFHSM0139 The amount of MVS storage available to CICS
  is critically low."  This is not the reason or cause for the
  loop, but it was seen in the reporting customer's case.  The
  trigger for the problem is MAXJVMTCBS or any of the other
  MAXxxxxTCBS values is reached, the new task is suspended while
  it waits for an OPEN TCB.  If the task is purged for any reason,
  the loop may occur.
  .
  The problem arises in DFHDSDS4 in SCAN_AWAIT_QUEUE: processing
  of await_tcb.  This is entered when CICS has reached MAXxxxxTCBS
  (in this case MAXJVMTCBS) and CICS needs to SUSPEND this latest
  task while it waits for an OPEN TCB.  If the SUSPEND exits
  normally then all is well.  But if the task is PURGEd for
  whatever reason, it is removed from the awaiting_open_tcb queue.
  If also this is the only TCB waiter then awaiting_open_tcb goes
  to zero and CICS completes await_tcb.  But OLDEST_AWAITER_TIME
  still has the STCK value from when the task entered the wait for
  a OPEN TCB.  This is detected in partition_exit where
  check_long_waiters is called and the STCK value causes
  notify_recommended = TRUE and this in turn results in the Call
  notify_dsti. notify_dsti issues the
  ?DFHTISRI
         FUNCTION(REQUEST_NOTIFY_IMMEDIATELY)
         TISRI_TOKEN(R_N_I_DEAD_TCBS_TOKEN)
  which immediately ATTACHs the DS system task to run
  PROCESS_DEAD_TCBS.  This repeats again and again causing the
  build up of over 5,000 DTAs.  When CHECK_EXECUTABLES next runs
  it will remove all these UNUSED DTAs.  But the ATTACHs will
  continue and the cycle begins again.  There are about 5000
  UNUSED DTAs and DS has a limit to prevent any more being created
  and this results in the trace entries indicating
  INSUFFICIENT_STORAGE:
  DSTCB QR DS 0004 DSSR ENTRY RESUME
  DSTCB QR DS 0005 DSSR EXIT  RESUME/OK
  TI    QR DS 0005 DSSR EXIT  SUSPEND/OK
  TI    QR DS 0002 DSAT ENTRY ATTACH
  TI    QR DS 0095 DSAT *EXC* TASK_GETMAIN_FAILURE
  TI    QR DS 0003 DSAT EXIT ATTACH/EXCEPTION INSUFFICIENT_STORAGE
  TI    QR TI 0162 TISR *EXC* NOTIFY-TASK-NOT-ATTACHED
  TI    QR DS 0004 DSSR ENTRY SUSPEND
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION: CICS loops after purging an open TCB    *
  *                      task.                                   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A system has reached MAXJVMTCBS and so any new JVM tasks have to
  be suspended waiting for a TCB to become free. During suspend
  one of these new tasks gets purged, either for dtimout or
  manually, and so the task has to be removed from the
  waiting_open_tcb queue. If this is the only TCB waiting then
  awaiting_open_tcb will drop to zero but OLDEST_AWAITER_TIME
  still has the STCK value from when the task was suspended. This
  causes notify_dsti to be issued repeatedly as it is not cleared,
  causing a slow down in CICS and eventually the DFHSM0139 message
  may be issued.
  
  Additional keywords: msgDFHSM0139
  

Problem conclusion

• Change DFHDSDS4 in routine SCAN_AWAIT_QUEUE to ensure that
  OLDEST_AWAITER_TIME is set correctly when a TCB is removed from
  the waiter queue.
  

Temporary fix

•             *********
              * HIPER *
              *********
  FIX AVAILABLE BY PTF ONLY
  

Comments

APAR Information

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

  PK02589

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

  UK04460

Modules/Macros

•    DFHDSDS4
  

Fix information

• Fixed component name

  CICSTS 3.1 Z/OS

• Fixed component ID

  5655M1500

Applicable component levels

• R400 PSY UK04460

     UP05/06/21 P F506

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.