PH48100: HIGH CPU UTILIZATION IN CSSMTP CHECKPOINT PROCESSING

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Each time a CSSMTP spool file processing thread creates an
  email, it calls the checkpoint program, EZAMLCKP, to register
  the email in a checkpoint record (CKPM).  EZAMLCKP unnecessarily
  scans through all of the thread's checkpoint records.  If the
  spool file contains thousands of emails, then the thread's CPU
  utilization grows exponentially as the number of checkpoint
  records increases causing the checkpoint record scans to become
  longer and longer.
  
  ANALYSIS:
  The mlCkpFindEmail function loops through every CKPM in every
  one of the JES thread's checkpoint blocks.
  
  KNOWN IMPACT:
  High CPU utilization.
  
  VERIFICATION STEPS:
  The "systrace perfdata" shows almost all of the CPU utilization
  is in the TCB for the JES thread the is processing the SYSOUT.
  The PSW report in the perfdata shows many iterations in
  EZAMLCKP's mlCkpFindEmail function.
  
  ADDITIONAL SYMPTOMS:
  High CPU
  

Local fix

• BYPASS/CIRCUMVENTION:
  Comment out the CHKPOINT DS in the CSSMTP JCL.
  
  RECOVERY ACTION:
  CPU utilization drops back to normal once all of the spool
  file's emails have been processed by the JES thread.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All users of the IBM Communications Server for z/OS Version  *
  * 2 Release 4 and 5 IP: CSSMTP                                 *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * High CPU utilization in CSSMTP checkpoint processing.        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A mail job spools a SYSOUT that contains hundreds of mails to
  CSSMTP.
  Each time the CSSMTP JES thread processes a mail, the checkpoint
  mail recorder unnecessarily scans through the entire checkpoint
  chain (every checkpoint email record in every checkpoint block)
  looking for a matching record.
  As more and more mails are processed, the checkpoint chain gets
  longer and longer causing the CPU usage to grow and grow.  The
  result is exponential growth in CPU utilization.
  

Problem conclusion

• The CSSMTP checkpoint program, EZAMLCKP, will no longer scan the
  checkpoint chain if the current mail is known to have not yet
  been recorded in the checkpoint area.  It will also only search
  through the checkpoint block that pertains to the current mail.
  

Temporary fix

Comments

APAR Information

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

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

  UI82172 UI82173

Modules/Macros

• EZAMLCKP
  

Fix information

• Fixed component name

  TCP/IP MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R240 PSY UI82172

     UP22/10/15 P F210

• R250 PSY UI82173

     UP22/10/15 P F210

Fix is available

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