For VTAM messages for a program operator

VTAM® uses the search order shown in Table 1.

Table 1. VTAM messages search order for a program operator
Program operator SSCPFM=USSNOP	Program operator SSCPFM=USSPOI
APPL definition statement	APPL definition statement
ISTINCNO	ISTCFCMM
	ISTINCNO

If no USS message is found, VTAM will issue USS message 14 to indicate that the message was not found. (USS message 14 is defined the same as IST458I in ISTINCNO.)

Note: Do not modify or replace the IBM-supplied default tables.

If no VTAM message is found, VTAM issues message IST998E to indicate that a VTAM message is not defined.

A VTAM message might be rerouted from the program operator application to the system console. A rerouted message will appear in the format as defined in the USS table designated for the VTAM operator based on the search order.

If a VTAM message is not completely defined in the first USS table searched, the next USS table in the hierarchy will be used. Because the IBM-supplied USS table (ISTINCNO) contains complete messages, you should define supplemental operation-level USS tables to specify only those parts of a message that you want to change. If VTAM cannot locate all the required parts of a message, it issues message IST998E to indicate that the message does not exist.