PH65446: CICS LIBERTY JVM SERVERS: CHANGES TO SERVER.XML EXECUTOR CORETHREADS SUPPORT.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• APARs PH51513 (CICS 5.6) and PH55687 (CICS 6.1) modified CICS
  so that for Liberty JVM servers a coreThreads value for the
  default executor threadpool was written by CICS into server.xml.
  This value was lower than the Open Liberty default calculation.
  
  The CICS coreThreads calculations used at CICS 6.2 and
  above were changed to use a higher number of coreThreads, so
  this APAR and PH65446 are taken to bring CICS 5.6 and 6.1 into
  line with CICS 6.2 and above.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: CICS 5.6 and 6.1 are out of step with   *
  *                      CICS 6.2 and higher in the setting of   *
  *                      coreThreads in a Liberty JVM server.    *
  ****************************************************************
  Bring CICS 5.6 and 6.1 into line with CICS 6.2 and above when
  starting a Liberty JVM server. This ensures that the number
  coreThreads to be used by Liberty is calculated the same from
  CICS 5.6 upwards. coreThreads are the minimum number of
  executor threads in Liberty that run the application workload.
  In addition, provide a JVM property to override the number of
  coreThreads calculated for use by Liberty.
  

Problem conclusion

• CICS has been modified so that coreThreads is now set to the
  lower of 12 or 2 * number of processors.  This replaces the
  previous calculation of the lower of 6 or 2 * number of
  processors.  This means that on systems with 4 to 6 processors
  the coreThreads value will increase.  coreThreads determines the
  minimum number of executor threads for application work to run
  on.
  The coreThreads value can be overridden using the
  com.ibm.cics.jvmserver.wlp.executor.corethreads JVM profile
  option.  This can be set to a number between 4 and 256, or wlp.
  If set to wlp, CICS will not specify a coreThreads value which
  means the server will use Liberty's default behaviour.  This
  property will be added to the 5.6 and 6.x documentation.  This
  option replaces the undocumented property
  com.ibm.cics.wlp.executor.corethreads added by PH51513.
  
  More information on the executor thread pool can be found in the
  Open Liberty documentation:
  https://openliberty.io/docs/latest/thread-pool-tuning.html
  
  The IBM Documentation for CICS TS 5.6 and 6.1 will be updated to
  document this new JVM property.
  

Temporary fix

Comments

APAR Information

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

  PH61224

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

  UO02851

Modules/Macros

• DFJ@H571
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UO02851

     UP25/04/18 P F504

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.