VTAM® operator commands entered by a program operator have the same format and effect as commands entered at the system console. The VTAM operator commands supported are the VARY, DISPLAY, and MODIFY commands. The REPLY command is also supported to answer VTAM messages that require a reply.

A program operator can issue all commands except the VTAM START and HALT commands; they can be issued only by the system operator at a system console. The MODIFY QUERY command can be issued only from a program operator application. For a description of MODIFY QUERY, see POA communication with tuning facility using the MODIFY QUERY COMMAND.

For information about each VTAM operator command that can be issued by the system operator, refer to z/OS Communications Server: SNA Operation. For additional information about VTAM operator commands that use the unformatted system services (USS) facility, refer to the z/OS Communications Server: SNA Resource Definition Reference.

A program operator application (POA) can open its ACB indicating that can receive the command complete message (IST1746I). VTAM issues this message as the last message in response to a VTAM operator command. After receiving this message, the POA continues processing with the next command. A POA must set this capability in vector list ISTVACBV-ISTVAC81. The flag is VAC81EOM. For further information, see the Application-ACB vector list (ISTVACBV).

The operating procedures supplied by the system programmer should not depend on internal VTAM execution sequences; that is, VTAM commands entered at nearly the same time could be processed in parallel, and the order of processing of the commands should not be assumed to be the same as the order in which the commands are entered. In particular, if one command depends on the successful completion of another, the dependent command should not be entered until the successful completion of the first command is confirmed by a VTAM message.