When session limits are set to 0, the sessions with the specified LU that is using the specified mode name (LU-mode) are deactivated. Sessions that are not needed currently are deactivated immediately. Sessions being used by a conversation are not deactivated until the conversation finishes. In addition, if draining was set on, draining now takes effect. For a description of when sessions are deactivated, see VTAM's role in session activation and deactivation.
If the application program requests 0 session limits on a CNOS negotiation, the session limits cannot be negotiated. The partner LU must accept 0 limits. At the time of this CNOS request to set session limits to 0 the application program can specify that the change is to apply to all mode names with the partner LU except the SNASVCMG mode. The application program does this by setting the NBRMODE (SLCALL) bit on in the CNOS session limits control block. (NBRMODE can be set to ALL only when session limits are being set to 0.) VTAM® can negotiate session draining responsibility and draining capability on the target side.
If the CNOS request is for all mode names and target side draining was specified, VTAM examines the negotiation value for each mode name and enables target side draining only for those modes whose negotiation value allows it. If the CNOS request specified that draining is not enabled on the target side, VTAM accepts that restriction without negotiation.