A fix is available
APAR status
Closed as program error.
Error description
A particular program is EXEC CICS LINKed or XCTL to very frequently, often multiple times per task. The tasks doing this are all running on their own Open TCB and there are ample logical processors in the LPAR so that these Open TCBs can indeed run concurrently. In an environment like this, if something causes many tasks to invoke the program at the same time, it is possible that the resulting contention for that program's Program lock can be great. It can be so great that invocations of this program are slowed so much that it becomes a bottleneck point that slows response time and decreases throughput. . In a dump taken during this situation, there will be lots of tasks either in LMQUEUE waits waiting for the PGLOCK or in PROGRAM waits all for the same program. The 'PGWE Summary' in PG=1 shows a significant number of PGWEs all for the same program.
Local fix
To break out of this situation, limit the number of concurrent tasks temporarily.
Problem summary
**************************************************************** * USERS AFFECTED: All. * **************************************************************** * PROBLEM DESCRIPTION: CICS slowed down when the same PROGRAM * * was LINK'd to concurrently by * * transactions running on open TCBs. * **************************************************************** * RECOMMENDATION: * **************************************************************** If a PROGRAM is locked, then a subsequent access of the same PROGRAM is SUSPEND'd and a PGWE is added to the PGWE chain. When the lock owner releases the lock, if there are any waiters, all the tasks on the PGWE chain for this PROGRAM are RESUME'd. Only one task can win the race for the PROGRAM lock and then all other tasks end up on the PGWE chain again. In a very busy CICS, when this happens, the resulting thrashing can be detrimental to task throughput. This problem is only exposed when the tasks are running on open TCBs. Keyword: PERFM
Problem conclusion
DFHPGCM release_program_lock has been changed to invoke a new refstep, resume_single_waiter.
Temporary fix
FIX AVAILABLE BY PTF ONLY
Comments
APAR Information
APAR number
PK58570
Reported component name
CICSTS V3 Z/OS
Reported component ID
5655M1500
Reported release
400
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2007-12-20
Closed date
2008-03-10
Last modified date
2008-04-01
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
PK60174 UK34404 UK34405
Modules/Macros
DESPGAI DESPGCM DESPGDD DESPGEX DESPGIS DESPGLD DESPGLK DESPGLU DESPGPG DESPGRP DFHPGAI DFHPGDD DFHPGEX DFHPGIS DFHPGLD DFHPGLE DFHPGLK DFHPGLU DFHPGPG DFHPGRE DFHPGRP DFHPGXE
Fix information
Fixed component name
CICSTS V3 Z/OS
Fixed component ID
5655M1500
Applicable component levels
Fix is available
Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.
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Document Information
Modified date:
01 April 2008