PM98645: MESSAGE SELECTION IMPROVEMENTS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Message selection improvements
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 7 *
  *                 Release 1 Modification 0.                    *
  ****************************************************************
  * PROBLEM DESCRIPTION: High cpu usage and/or bufferpool paging *
  *                      activity when using Message Selection   *
  *                      on queues with a large number of        *
  *                      non-matching messages.                  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A task attempting to get a message from a queue using message
  selection scans each message on the queue to identify the first
  matching message to return. Each non-matching message is marked
  as such, so that the selector is not reevaluated.
  If no matching messages are found, subsequent scans of the queue
  will look at each message again to determine if they match,
  however prior to identifying that the message is already marked
  as not matching the selector, CSQIVALM loads the IRH9 page for
  the message.
  If the message does not match, this IRH9 page is not needed,
  and if there are a large number of non-matching messages,
  loading the IRH9 page for each message puts additional
  unnecessary stress on the bufferpool, potentially leading to
  increased paging activity.
  The problem is further exposed when message marking is also
  in use (for example, when the task is an MDB).
  In this instance, whenever the coop mark on a message expires,
  all handles on the queue are posted, and will rescan the
  queue, leading to further unnecessary IRH9 pages being loaded.
  

Problem conclusion

• CSQIVALM is changed to check if a message has already been
  evaluated against the selector and found not to match prior to
  loading the IRH9 page.
  CSQMMTIN is changed so that when the coop mark expires for a
  message, only handles that haven't marked that message as not
  matching their selector are posted.
  100Y
  CSQIVALM
  CSQMDALL
  CSQMGET
  CSQMLTR0
  CSQMMTIN
  CSQMMTPR
  CSQM1PAW
  

Temporary fix

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

Comments

APAR Information

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

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

  UI13086

Modules/Macros

• CSQIVALM CSQMDALL CSQMGET  CSQMLTR0 CSQMMTIN
  CSQMMTPR CSQM1PAW
  

Fix information

• Fixed component name

  WMQ Z/OS V7

• Fixed component ID

  5655R3600

Applicable component levels

• R100 PSY UI13086

     UP13/12/24 P F312 Ž

Fix is available

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