There are a number of conditions under which the thread is executing in the control region. These include, but are not limited to:
I/O to ISAM files
EOV processing on all database datasets (when required to free up a buffer)
Users issuing large numbers of IMS commands Services Fast Path Wait For Input (WFI) GU calls Create and terminate thread processing Complete sync-point processing
ISWITCHed to Fast Path TCB
The collector found that the thread executed an ISWITCH macro. The thread is still executing, but in the control region under the Fast Path TCB.
ISWITCHed to LSO
The collector found that the thread executed an ISWITCH macro. The thread is still executing, but in the control region instead of the CICS region. The ISWITCH was done using the Local Storage Option (LSO).
For LSO=Y, instead of running in the control task, the thread is running under a subtask in the control region that is reserved for its use only. LSO=Y costs a substantial amount of CPU, but saves virtual storage in CSA at the cost of virtual storage in the private area of the IMS control region.
IWAIT in IMS Dispatcher
IWAIT in IMS dispatcher is a measure of the IMS dispatching queue for CICS region activities. The collector found the thread IWAITing in the IMS dispatcher and could not attribute the condition to any of the DL/I oriented states listed earlier in this chapter.
As the workload rises, this value also rises. This number should be small.
IWAIT in Term
The collector found the thread IWAITing. It also found an indication that the application program was terminating. The collector could not attribute the status of the thread to any of the states listed earlier in this chapter.
Note: This execution state should be small. Termination IWAITs may be attributed to sync point processing of an update thread.