A fix is available
APAR status
Closed as program error.
Error description
Excessive POST calls are observed when internal queue manager trace is active on a system with a large number of connected applications. Change Team determined that performance is impacted such that applications may experience slower response times. Transmission queue backlogs were also observed. . Additional keywords: CML LOCL lock
Local fix
Increase the maximum number of trace blocks using for example /cpf RECOVER QMGR(TUNE TABMAXBLK 10240) where "cpf" is the command prefix for the queue manager. The blocks are 8KB in size, so a setting of 10240 will require 80MB of storage. This is taken from the 64 bit address range above the bar, so it should not cause a storage problem. The TABMAXBLK value is not preserved over a queue manager restart, so you can include the RECOVER QMGR command in a CSQINP2 member minus the "/cpf" syntax.
Problem summary
**************************************************************** * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 7 * * Release 1 Modification 0. * **************************************************************** * PROBLEM DESCRIPTION: When running with MQ MSTR trace active * * on a busy system, a high volume of post * * calls can occur causing performance * * degradation due to lock contention. * **************************************************************** * RECOMMENDATION: * **************************************************************** If MQ trace is started with TRACE(GLOBAL) and DEST(RES), the queue manager trace is written to a 64 bit storage area in the MSTR address space. The storage area is split into blocks which are used by individual tasks to capture their trace. On a queue manager where there are sufficient connections to cause all the blocks (1024 by default) to be in use, some tasks will not have a trace block available. For these tasks, on each trace call a check is be made to see if a block is available. If not, the trace data is written to the shared trace storage in ECSA. During the check for available blocks, a post call is made to a worker task in the MSTR address space. The LOCAL/CML lock is required to complete the post. The frequency of post calls from multiple tasks can result in contention for the LOCAL/CML lock. This can cause slow response times and increased CPU usage for applications making MQ API calls.
Problem conclusion
Trace processing has been modified to reduce the frequency of post calls and relieve the LOCAL/CML lock contention. 100Y CSQMSNTF CSQWVGSG
Temporary fix
********* * HIPER * *********
Comments
APAR Information
APAR number
PI55911
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
2016-01-22
Closed date
2016-02-10
Last modified date
2016-06-14
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI35205
Modules/Macros
CSQMSNTF CSQWVGSG
Fix information
Fixed component name
WMQ Z/OS V7
Fixed component ID
5655R3600
Applicable component levels
R100 PSY UI35205
UP16/03/03 P F603 ¢
Fix is available
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Document Information
Modified date:
14 June 2016