A fix is available
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 7 * * Release 0 Modification 1 and Release 1 * * 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. 010Y 100Y CSQRSHUN
Temporary fix
********* * HIPER * *********
Comments
APAR Information
APAR number
PI28301
Reported component name
WMQ Z/OS V7
Reported component ID
5655R3600
Reported release
010
Status
CLOSED PER
PE
NoPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2014-10-23
Closed date
2015-03-20
Last modified date
2015-05-04
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
PI36869 UI26134 UI26135
Modules/Macros
CSQRSHUN
Fix information
Fixed component name
WMQ Z/OS V7
Fixed component ID
5655R3600
Applicable component levels
Fix is available
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Document Information
Modified date:
04 May 2015