Sources of start options

When VTAM® is started, you can provide the options from any combination of the sources listed below (arranged from the lowest to highest priority):

IBM-supplied values internal to VTAM (default values).
Default start option list. When you start VTAM, a list of user-defined default values (ATCSTR00) is read from the VTAM definition library. If VTAM cannot find the ATCSTR00 file, it prompts you, giving you a choice of:
- Using default values
- Using an alternate start option file (ATCSTRxx, where xx specifies the identifier of the start option file you want to use)
- Canceling the start attempt
If you do not want to use the ATCSTR00 file, you can avoid the prompt by coding an ATCSTR00 file that contains only comments. VTAM issues a message that the file is empty, but does not interrupt start processing.
Supplemental start option list. The VTAM operator can enter the LIST=xx start option on the START command to name another list to supplement ATCSTR00. The supplemental list (ATCSTRxx) can override options in the default ATCSTR00 list, and the IBM-supplied internal default values.
Backup start option list. The LISTBKUP start option can be placed in a start list (ATCSTR00 or ATCSTRxx) to indicate the processing that occurs if a start option in the list is not valid. You should place the LISTBKUP start option first in a start list, so that it will have been processed if an error is found for another start option.
Start options entered by the operator. The VTAM operator can enter additional start options on the START command, and also during VTAM startup if prompted. (VTAM prompts for start options if the operator does not enter any start options on the START command.) To prevent VTAM from prompting for start options during startup, code the NOPROMPT option in ATCSTR00.
Start options entered by the operator can override options in a specified supplemental start option list, and start options in the default ATCSTR00 list and the IBM-supplied internal default values.

To enter a list of options longer than the length of the console, place a comma after the last start option that will fit on the console and VTAM will continue to prompt for more start options.
Start options reentered by the system operator to correct errors in previously processed start options.