Start option processing

In Sources of start options the list of start option sources is arranged from the lowest priority to the highest. VTAM® processes the start options with the lowest priority first and those with the highest priority last. If conflicting specifications exist for a particular start option, the last valid specification entered always overrides any previous specification. For example, if ATCSTR00 contains CONFIG=01, but the operator enters LIST=ST and ATCSTRST contains the start option CONFIG=02, VTAM activates the configuration defined by ATCCON02.

If VTAM detects an error when reading in a start option list, it notifies the operator. The operator must then do one of the following actions:

Respond to the error message by selecting the "continue processing" option and then reenter any start options that were specified incorrectly in the start option list. The operator can also enter additional options at this time.
Specify a different start option list to use by entering xx (for the required ATCSTRxx start option list). This cancels the start attempt and then begins start processing again with another start option list.
Halt VTAM. This cancels the start attempt so that you can correct the start option list and try again.

After reading in a start option list, if VTAM detects an error while processing a specific start option, the following condition occurs:

Backup processing occurs if the LISTBKUP start option was processed and the start list in error is not a backup start list (only one backup start list can be processed).
If the LISTBKUP start option was not processed, the operator is provided with the same three choices available when VTAM encounters an error while reading in a start list.

Use the LISTBKUP start option to specify:

Another start list should be used in place of the start list in error (LISTBKUP=xx).
All start option values existing before the file in error was processed should be used (LISTBKUP=DEFAULTS).
All valid start options in the file in error will be processed, and incorrectly specified start options should remain as previously set until VTAM reprompts for these options (LISTBKUP=PROMPT).