PH68124: REDUCE OVERHEAD OF RUNAWAY DETECTION OF TASKS RUNNING ON T8 TCBS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• CICS' runaway detection mechanism uses the z/OS STIMERM macro to
  periodically check if a task may be looping.  On idle systems
  with thousands of T8/threads in Liberty JVM server thread pools
  this may cause a noticeable CPU overhead.  This APAR will reduce
  the frequency at which CICS checks if a task may be looping when
  running on a T8 TCB.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: The CPU overhead of CICS' runaway       *
  *                      detection mechanism may be noticeable   *
  *                      on an idle system with many T8          *
  *                      TCBs/threads for Liberty JVM servers.   *
  ****************************************************************
  Many Liberty JVM servers are enabled across multiple CICS
  regions.  The Liberty JVM servers are idle with no workload to
  process.
  
  Following PH61224/PH65446 the number of T8 TCBs /
  threads in each idle Liberty server's thread pool defaults
  algorithmically.
  
  However if JVM profile option
  com.ibm.cics.jvmserver.wlp.executor.corethreads has been set to
  increase the minimum number of threads per pool there may be
  many T8 TCBs/threads in existence across the regions.
  
  CICS' runaway detection mechanism uses the z/OS STIMERM macro to
  periodically check if a task may be looping.  On systems with
  a large number of T8 TCBs/threads this may cause a noticeable
  CPU overhead.
  

Problem conclusion

• CICS' runaway detection mechanism has been updated to reduce the
  CPU overhead.
  

Temporary fix

Comments

APAR Information

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

  PH67350

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

  UO05382 UO05383 UO05384

Modules/Macros

• DFHKETIX
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UO05384

     UP25/10/18 P F510 ¢

• R500 PSY UO05383

     UP25/10/21 P F510 ¢

• R600 PSY UO05382

     UP25/10/18 P F510 ¢

Fix is available

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