gtpi1m1r | System Installation Support Reference |
User exit routine UCCTHR is provided as a default for processing a record
cache subsystem (RCS) I/O queue threshold exceeded condition. This exit
point, which is nondynamic, is invoked by entry point CJIVTTMR in control
program CSECT CCRCSC whenever the I/O queue threshold value computed for an
RCS subsystem is exceeded.
This user exit provides I/O queue depth statistics for a degraded record
cache subsystem (RCS) controller on a periodic basis whenever a calculated
threshold value is exceeded for the subsystem. System processing action
depends on the action specified by the user exit in the thresholding parameter
list provided.
An interface parameter list (IDSTHR) is provided by CJIVTTMR that passes
relevant queue depth information. CJIVTTMR accepts the processing
action that the user specifies in the parameter list on return.
General Conditions at Entry
The registers at entry to UCCTHR are:
- R6
- IDSTHR parameter list.
- R11-R15
- See User Exit Routines - Common Entry Conditions.
System Conditions at Entry
- System state
- Supervisor
- System mask
- Unmasked
- Protect key
- 0
- Address space
- SVM.
Programming Considerations at Entry
- The parameter list IDSTHR is provided so the control program is the only
code that is required to understand the internal system data
structures. Because a menu of processing options is provided, you do
not have to be aware of the internal data structures and, therefore, should
not need to change them because of system changes.
- Return must be made to CJIVTTMR because that entry point restarts the
periodic (1 second) timer interval for threshold monitoring.
- See User Exit Routines - Common Entry Conditions.
- See User Exit Routines - Common Programming Considerations for other considerations.
Programming Considerations on Return
- R14 will contain a return code, set by the user exit routine, that will
show what action is to be taken. The following return code definitions
are supported:
- 0 - No action required
- 4 - Prime w/longest queue is down
- 8 - Mod w/longest queue is down
- 12 - Turn thresholding off
- 16 - Change threshold value
- 20 - Dupe w/longest queue is down
- See User Exit Routines - Common Return Conditions.
General Conditions on Return
See User Exit Routines - Common Return Conditions.