You can modify certain messages and operator commands. These commands and messages are defined in unformatted system services (USS) tables and are called USS messages and USS commands. Whenever VTAM® receives a USS command, it uses either an IBM-supplied default USS table or a user-written USS table to process it. Similarly, whenever VTAM is to send a USS message, it uses one of these tables to determine the message level (the message associated with this release of VTAM or a previous release), message text, and other characteristics of the message. The IBM-supplied operation-level USS table is named ISTINCNO.

By creating a supplementary USS table, you can change the text or other characteristics of a message or the syntax or default values for a command. You can create supplementary tables using USS macro instructions to redefine the VTAM commands or messages that you want to change. To use your USS table, specify the name of the table on the USSTAB start option. If you specify a user-defined table for operator commands, the ISTINCNO table is not used. If you specify a user-defined table for operator messages, the ISTINCNO table is used in conjunction with the user-defined USS table. For more information about USS tables, see the z/OS Communications Server: SNA Resource Definition Reference.

You can specify an operation-level USS table for a program operator using the SSCPFM and USSTAB operands of the program operator APPL definition statement.