gtpi1m2n | System Installation Support Reference |
User exit routine UCCWAI is called at the beginning of macro processing for
the WAITC macro (if the exit point named WAI is active).
Exit point WAI is in CSECT CCNUCL.
General Conditions at Entry
The registers at entry to UCCWAI are:
- R0-R7
- Contents as set by the program that issued the WAITC macro.
- R8
- Base of E-type program that issued the WAITC.
- R9
- Address of the ECB.
- R11-R15
- See User Exit Routines - Common Entry Conditions.
System Conditions at Entry
- System state
- Problem (see Programming Considerations at Entry, item 1)
- System mask
- Unmasked (see Programming Considerations at Entry, item 1)
- Protect key
- Working storage or zero (0)
- Address space
- EVM.
Programming Considerations at Entry
- Usually, the system state and system mask are as
stated. However, there can be exceptions if system programs issued
MONTC to get to supervisor state and changed the system mask.
- The WAI exit point occurs before checking the I/O count in the ECB.
Therefore, the I/O count is unknown at entry to user processing.
- See User Exit Routines - Common Entry Conditions.
- See User Exit Routines - Common Programming Considerations for other considerations.
Programming Considerations on Return
See User Exit Routines - Common Return Conditions.
General Conditions on Return
- If the I/O counter is zero (no I/O is pending) when UCCWAI returns to the
NSI in WAITC macro processing, no other user exit routines are invoked and
control is returned to the E-type program that issued the WAITC. If the
I/O counter is not zero (I/O is pending) when UCCWAI returns to the NSI, the
MONWC macro causes the user exit routine at label UCCSVC to run. When
all I/O is complete for the ECB, UCCSVW is run at post interrupt time (if the
SVW exit point is active) and control is returned to the E-type program that
issued the WAITC.
- See User Exit Routines - Common Return Conditions.