gtpi1m2nSystem Installation Support Reference

WAITC Macro Entry

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

  1. 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.
  2. 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.
  3. See User Exit Routines - Common Entry Conditions.
  4. 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

  1. 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.
  2. See User Exit Routines - Common Return Conditions.