PI36869: WMQ HUNG AND USING CONSIDERABLE AMOUNT CPU DUE TO ARCHIVE LOG FILLING UP WITH CSQJ003I +SSID FULL ARCHIVE LOG VOLUME

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• The customer experienced an outage on a production
  WMQ region.  WMQ was using considerable amount CPU
  and having a problem with the archive log files.
  In the MSTR log, there were many
  CSQJ003I +SSID FULL ARCHIVE LOG VOLUME messages.
  There was a large number of expired messages on the
  queue. The client channels had issued MQGETs against
  the queue, and the MQGET was processing finds/deletes
  of the expired messages.
  The messages on queue were persistent, and log
  records were written for the expired messages,
  which caused the active logs dataset to fill up.
  An SVCDUMP taken and there were over 1 million messages
  on the queue and most of them had expired or were about
  to expire.
  To make matters worse, the queue-manager has a relatively
  low value for LOGLOAD (10,000),which meant that the
  queue-manager was checkpointing very frequently due
  to the log records for the expiry of the messages.
  .
  Additional Symptom(s) Search Keyword(s):
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 8 *
  *                 Release 0 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Shunted units of work contain           *
  *                      unnecessary log records, leading to an  *
  *                      increase in log usage and checkpoint    *
  *                      frequency.                              *
  *                      In rare cases, if LOGLOAD is set to a   *
  *                      low value, the additional logging for   *
  *                      large units of work requiring shunting  *
  *                      can trigger further shunting, resulting *
  *                      in the queue manager being unable to    *
  *                      perform further non-shunt related       *
  *                      logging.                                *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  While processing long running units of work, CSQRSHUN will
  'shunt' the log records associated with those units of work to
  the current active log, so that if undo processing is required,
  it will not need to go back to the original archived log
  records.
  However, there are situations where log records in a unit of
  work are not required for undo processing - for example, when
  out of suncpoint work has taken place on the same task, or
  when expired messages are identified during browse or get
  processing. In these cases a compensating log record is
  written to identify which records are not needed for undo
  processing, however these records will still be shunted by
  CSQRSHUN.
  These records increase the number of records that are written
  each time the unit of work is shunted. In some cases, where
  the number of these records is very high (for example, when
  getting from a queue with a large number of expired messages)
  the amount of log space required to shunt these records leads
  to an increase in checkpoint frequency and performance
  degradation.
  

Problem conclusion

• CSQRSHUN is changed to no longer shunt log records for which a
  compensating log record exists, and which consequently are not
  needed for undo processing.
  000Y
  CSQRSHUN
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

  PI28301

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

  UI26136

Modules/Macros

• CSQRSHUN
  

Fix information

• Fixed component name

  WMQ Z/OS 8

• Fixed component ID

  5655W9700

Applicable component levels

• R000 PSY UI26136

     UP15/04/16 P F504 ¢

Fix is available

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