Although application programs cannot explicitly establish and terminate LU 6.2 sessions, they do take actions that result in sessions being established or terminated. Most of these actions involve controlling the session limits between an application program and a partner LU for a given mode name.

An application program uses the APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS macroinstruction to set new session limits for sessions between itself and another LU using a specified mode name. These new session limits can cause VTAM® to activate or deactivate sessions for the application program. However, the application program has no control over which particular session is activated or deactivated.

The session limits apply to a given mode name. An application program can set new session limits with a partner LU for a mode name of EXAMPLE and can leave session limits unchanged for other mode names for the same LU. Session limits for a mode must be negotiated before VTAM can activate a session on that mode.

See Managing sessions for a discussion of the interaction of session limits, the CNOS macroinstruction, and session activation and deactivation.