A fix is available
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 number
PM98645
Reported component name
WMQ Z/OS V7
Reported component ID
5655R3600
Reported release
100
Status
CLOSED PER
PE
NoPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2013-10-08
Closed date
2013-11-29
Last modified date
2014-01-02
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
Fix is available
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Document Information
Modified date:
02 January 2014