Unformatted system services tables

VTAM® uses unformatted system services (USS) tables to:
  • Issue messages to the VTAM operator console or a program operator application
  • Process VTAM operator commands
  • Issue messages to a terminal operator user
  • Process commands received from a terminal operator user

Other messages, such as TSO/VTAM messages, are provided through other facilities. For an explanation of these messages, see z/OS Communications Server: SNA Messages.

VTAM uses two types of USS tables to define messages and commands:
Session-level table
Contains:
  • Definitions for terminal user commands (such as LOGON) that can be received from a terminal.
  • Messages that VTAM sends to a terminal.
  • A translation table that is used for character-coded input from the terminal.
See Session-level USS table (ISTINCDT) for an example of a session-level USS table.
Operation-level table
Contains USS commands (such as DISPLAY ROUTE) that can be received from the VTAM operator or a program operator application and messages issued in response to those commands. See Operation-level USS table (ISTINCNO) for an example of an operation-level USS table.

IBM® supplies default USS tables with the VTAM product. The source language for these tables is contained in SYS1.ASAMPLIB. Table 1 describes the default tables.

Table 1. Description of the IBM-supplied USS tables
Table name Description
ISTINCDT Default session-level USS table used by terminal operator users. Contains the following items:
  • The following terminal operator commands:
    • LOGON
    • LOGOFF
    • IBMTEST
  • USSMSGxx (where xx equals 1–9 and 11–14) that are sent to a terminal operator. See z/OS Communications Server: SNA Messages for detailed descriptions of USS messages.
  • Translation table that is used for character-coded input from the terminal. The translation table, named STDTRANS, converts lowercase characters to uppercase and converts horizontal tabs to spaces.
ISTINCNO Default operation-level USS table used by the VTAM operator (commands and messages) and program operator applications (commands). Contains the following items:
ISTCFCMM Default operation-level USS table for a program operator application containing operation-level VTAM messages.