A fix is available
APAR status
Closed as program error.
Error description
A CICSPlex SM Sysplex Optimised Workload shares region status data in the z/OS coupling facility with access controlled by a coupling facility data table (CFDT) server. This information describes the health status and load of each region participating in the workload. Target regions typically update their own record in this CFDT when the current task load crosses certain tier boundaries. The size of these boundaries is controlled by the UPDATERS setting. The size of the lowest boundary is controlled by the BOTRSUPD setting, which by default is 1% of MXT. For CICS regions running with a very high MXT setting, which spend a significant amount of time operating below 1% of MXT, this may result in an unusually high rate of updates to coupling facility data table DFHRSTAT.
Local fix
Problem summary
**************************************************************** * USERS AFFECTED: All users of CICSPlex SM V5.4, V5.5, V5.6. * **************************************************************** * PROBLEM DESCRIPTION: CICS regions using CICSPlex SM * * Optimised Workload Management with * * a high MXT value but low number of * * concurrent tasks may result in high * * rate of coupling facility data table * * DFHRSTAT updates. * * This occurs when WLM target regions * * spend a significant amount of time * * operating below the BOTRSUPD threshold. * **************************************************************** * RECOMMENDATION: After applying the PTF resolving this APAR, * * all target regions must be restarted to * * pickup the changes. Note that the restarts * * do not need to occur at the same time. * * * * Target regions wishing to exploit the new * * function should specify new feature toggle: * * com.ibm.cics.cpsm.wlm.botrsupd.enabled=false * * however a tuning exercise should first * * be undertaken to assess the number of * * target regions available, the MXT values, * * and the expected level of work. * **************************************************************** When using CICSPlex SM Sysplex Optimised Workload Management, every task load change below the BOTRSUPD threshold in a target region will cause an update to the CICS region status (RS) server (DFHRSTAT). The default value for BOTRSUPD is 1% of the MXT value; this is also the minimum value. Therefore, CICS regions running with a high MXT setting, and a consistently low number of concurrent tasks may result in a high rate of updates to the CICS RS server.
Problem conclusion
A new feature toggle has been added to let users control whether or not to update the CICS RS server when the task load remains below the BOTRSUPD threshold. The new feature toggle is: com.ibm.cics.cpsm.wlm.botrsupd.enabled = { TRUE | false } The default setting (true) will maintain the current behaviour. When this feature toggle is set to false, then DFHRSTAT will not be updated for task load changes below the BOTRSUPD threshold. The apparent task load (ROUTINGLOAD as seen through the WLMATARG resource table) will remain at zero tasks, until the first boundary defined by the UPDATERS setting is reached. Note that if only a subset of target regions within a workload are run with com.ibm.cics.cpsm.wlm.botrsupd.enabled=false, then those regions may take a greater proportion of the workload. The feature toggle is only meaningful in a MAS which is a target region in an active workload. In all other contexts it will be ignored. Modules DFHRSDC, DFHRSDM, DFHRSXM have been updated to support this new feature. The Knowledge Center for CICS Transaction Server for z/OS Version 5 Release 4, Version 5 Release 5, and Version 5 Release 6 will be updated. A new entry will be added to the 'Changes to toggle-enabled' features topic. Feature Name: Disable updates to the coupling facility (CF) due to BOTRSUPD, Feature Toggle: com.ibm.cics.cpsm.wlm.botrsupd.enabled={TRUE|false} V5.4/5.5/5.6: APAR PH14812. The default is true. The 'Region status server, bottom-tier parameter (BOTRSUPD)' topic will be updated to describe the new toggle. A new section will be added: Disabling updates to the CF due to BOTRSUPD You can set the following feature toggle to disable updates to the Coupling Facility when the task load falls below the lower tier threshold. com.ibm.cics.cpsm.wlm.botrsupd.enabled=false The lowest possible setting for BOTRSUPD is 1%. Therefore, regions with a high MXT setting, which spend a significant amount of time operating below 1% of their declared capacity, might perform a high number of CF updates. With this feature toggle in effect, when the task load for a region falls within the BOTRSUPD range, no updates will be made to the CF. The task load value stored in the CF will remain zero until the first task load boundary defined by the UPDATERS parameter is reached. Note that if only a subset of target regions within a workload are run with com.ibm.cics.cpsm.wlm.botrsupd.enabled=false, then those regions may take a greater proportion of the workload.
Temporary fix
Comments
APAR Information
APAR number
PH14812
Reported component name
CICS TS Z/OS V5
Reported component ID
5655Y0400
Reported release
100
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2019-07-23
Closed date
2020-08-07
Last modified date
2020-09-01
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI70941 UI70942 UI70943
Modules/Macros
DFHRSDM DFHRSDUF DFHRSSR DFHRSXM
Fix information
Fixed component name
CICS TS Z/OS V5
Fixed component ID
5655Y0400
Applicable component levels
R100 PSY UI70943
UP20/08/11 P F008
R200 PSY UI70942
UP20/08/11 P F008
R300 PSY UI70941
UP20/08/11 P F008
Fix is available
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Document Information
Modified date:
02 September 2020