A fix is available
APAR status
Closed as program error.
Error description
You see dispatch wait time (DISPWTT) is higher than the suspend time (SUSPTIME) for some transactions. This problem has been tracked to a problem updating the DISPWTT field during a TCB switch. These are different from normal suspends because you don't need to wait for a resource. In a normal suspend, we would pop the task off the TCB it is running on, suspend the task (and start the SUSPTIME clock). Then later the resource you are waiting for would become available. The task then gets made dispatchable, and put on the dispatchable chain of its TCB. We start the DISPWTT clock at this point. A change mode is different in that there is no real resource being waited for. The task is put onto the dispatchable queue of its new TCB right away, so all of the time for which it is "suspended" is time waiting for its new TCB. A problem with the way the calculation is performed for a TCB CHANGE_MODE meant that the amount added to DISPWTT is actually very very slightly larger than the amount added to SUSPTIME. You would expect it would be exactly the same, or perhaps very very slightly smaller. This means that in a workload that does a very large number of TCB switches, relative to the amount of time spent in a 'real' suspend, it is possible for the DISPWTT time to catch up to, and overtake the SUSPTIME. I think a more normal workload with real suspends in it would never encounter this issue, and this is why it only hit it on certain transactions. Additional Symptom(s) Search Keyword(s): KIXREVSVR
Local fix
Problem summary
**************************************************************** * USERS AFFECTED: All CICS Users. * **************************************************************** * PROBLEM DESCRIPTION: Monitoring field DISPWTT can have * * a value that is greater than the * * SUSPTIME field value. * **************************************************************** * RECOMMENDATION: * **************************************************************** When performance monitoring is turned on, a task that is entering dispatcher due to a change tcb mode request or a change priority request will result in the amount added to the Dispatch Wait Time (DISPWTT) value being greater than the amount added to the Task Suspend Time (SUSPTIME). It is stated in the knowledge center that the SUSPTIME includes the value of the DISPWTT field. The DISPWTT field is calculated by noting the time when a task is made dispatchable and then using this with the dispatch start time to figure out how long the task was waiting to be dispatched. The dispatch start time is also used to stop the clock that records the SUSPTIME. However, the field used to note the time when the task is made dispatchable is not updated at this point and was last used just before the task suspended. This has resulted in the DISPWTT value being greater than the corresponding SUSPTIME. Additional Keywords: 014 102 ENQUEUE_TIME WAIT_FOR_REDISP DISPATCH_START TMA_DFHTASK_014 TMA_DFHTASK_102
Problem conclusion
DFHDSTCB has been updated to ensure that ENQUEUE_TIME is updated when a task is made dispatchable for a change_mode or change_priority request.
Temporary fix
FIX AVAILABLE BY PTF ONLY
Comments
APAR Information
APAR number
PI56728
Reported component name
CICS TS Z/OS V4
Reported component ID
5655S9700
Reported release
600
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2016-02-05
Closed date
2016-04-19
Last modified date
2016-05-04
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Modules/Macros
DFHDSTCB
Fix information
Fixed component name
CICS TS Z/OS V4
Fixed component ID
5655S9700
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:
04 May 2016