Debugging IPCS REXX EXECs

IPCS provides attention processing for its host command environment. The attention processing makes available all of the REXX debug aids from an interactive IPCS session. During processing of an IPCS REXX EXEC, you can press the attention interrupt key to use the debug aids in attention mode.

The attention processing handles IPCS subcommands differently depending on the mode.

In IPCS line mode, subcommands run to completion before an immediate command takes effect.
In the IPCS dialog, the HI immediate command ends both the subcommand and the EXEC. For all other immediate commands, the IPCS subcommands run to completion before the immediate command takes effect.

For example, suppose you press the interrupt key while a REXX EXEC is running the SUMMARY subcommand. The system reacts as follows:

If the EXEC is run in IPCS line mode, the system displays message IRX0920I:
```
ENTER HI TO END, A NULL LINE TO CONTINUE, OR AN IMMEDIATE COMMAND
```
You respond by entering the HI immediate command. Because the SUMMARY subcommand has not completed processing, the system completes processing of the subcommand before ending the EXEC.
If the EXEC is run in the IPCS dialog, the system displays the following message:
```
Enter HI to end, a null line, TIME, or an immediate command
```
You respond by entering the HI immediate command. The system ends the subcommand and the EXEC.

See z/OS MVS IPCS Commands for information about attention processing in IPCS and z/OS TSO/E REXX Reference for descriptions of the REXX debug aids.