Logon and logoff requests from dependent logical units

To request a session with an application program, an LU sends a logon request to VTAM® specifying the application program name and, optionally, a logon mode name and some additional information. Logon and logoff requests can be field-formatted SNA Initiate® and Terminate requests, which are built by the logical unit that sent them, or they can be (unformatted) character-coded commands, which are translated by VTAM into a field-formatted SNA request. VTAM uses session-level USS tables and interpret tables to do the translation.

A session-level USS table can be used to convert the USS command into a field-formatted SNA request. If a character-coded command violates the USS command syntax rules (see the z/OS Communications Server: SNA Resource Definition Reference), an interpret table must be used for the conversion.

You can customize VTAM to accept other character-coded commands by coding an interpret table. The following forms of requests make use of the interpret table to determine the name of the application program to which the request is being made:

A field-formatted SNA request received directly from a logical unit
An unformatted character-coded command, converted to a formatted SNA request

For example, any of the above forms of a request can indicate a logon to APPL01, and the interpret table can change APPL01 into TESTAPL1.

You associate an interpret table to a logical unit using the LOGTAB operand on the LU definition statement. You associate a USS table to a logical unit using the USSTAB operand on the LU definition statement.

For a complete description of operation- and session-level USS tables, see the z/OS Communications Server: SNA Resource Definition Reference.