PI22617: JVM SERVER DEADLOCK OCCURS WHEN REDUCING THREADLIMIT

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The JVM server thread limit was originally set to 100.  While
  the workload was running with 100 active threads, CEMT was used
  to reduce the threadlimit to 50.  The CEMT transaction acquires
  the JVMSRVLK and becomes stuck in a DISPATCH THR_POOL wait
  waiting for a T8 TCB to become available.  It does not release
  the JVMSRVLK which results in several other transactions (CJSA
  tasks) backing up waiting to acquire the JVMSRVLK.
  
  The CEMT task successfully changed the THREADLIMIT of the JVM
  to 50 and the corresponding maximum number of T8 TCBs to 51 (to
  allow space for a system T8).  However, there are currently 98
  T8 TCBs in use by the current workload which need to drain out
  of the system.
  
  
  
  
  
  
  
  
  Additional Symptom(s) Search Keyword(s): KIXREVCTC
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: THR_POOL wait not resumed when reducing *
  *                      the JVM server threadlimit.             *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  CEMT was used to reduce the JVM server threadlimit in a region
  running with more active threads than the new limit.
  The CEMT task acquired the JVMSRVLK lock in exclusive mode and
  DFHSJTH issued a DFHDSAT CHANGE_MODE request to switch to a
  T8 TCB. This suspended with a THR_POOL wait for a T8 TCB to
  become available.
  The active threads were unable to complete and release T8 TCBs
  because they needed to obtain the JVMSRVLK lock and deadlock
  occurred.
  

Problem conclusion

• DFHSJTH is changed to release the JVMSRVLK lock when issuing the
  DFHDSAT CHANGE_MODE request to switch to a T8 TCB.
  

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:

  UI21722 UI21723 UI21724

Modules/Macros

• DFJ@H360
  

Fix information

• Fixed component name

  CICS TS Z/OS V5

• Fixed component ID

  5655Y0400

Applicable component levels

• R90D PSY UI21723

     UP14/10/08 P F410

• R900 PSY UI21722

     UP14/10/08 P F410

• R903 PSY UI21724

     UP14/10/08 P F410

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.