Using CNOS, an LU 6.2 session partner can request that the session limits be set to 0. Then, the sessions that are active and not used for a conversation are deactivated. The LU partner that is responsible for deactivating the sessions for a given mode name is determined by an indicator in the CNOS request. The DRESPL operand on the APPL definition statement can be used to indicate if the VTAM® application program accepts the responsibility for deactivating the sessions (ALLOW) or if VTAM assigns that responsibility to the partner LU when the CNOS request is sent (NALLOW).

When sessions between partner LUs are to be deactivated, the existing conversations are not disrupted, but subsequent allocation requests for conversations can be queued. Before deactivating the sessions for a given mode name, the partner LUs can indicate whether conversations that are queued for a session are to be processed or discarded. The DDRAINL operand on the APPL definition statement indicates whether the VTAM application drains the queued allocation requests when deactivating sessions. If you code DDRAINL=ALLOW, the conversations that are queued for a session for the given mode name are processed before deactivating the sessions. If you allow conversations to be drained, new conversations are allocated a session if the allocation request occurs before the deactivation of all of the sessions for the given mode name. If you code DDRAINL=NALLOW on the APPL definition statement, VTAM does not allow the application program to drain queued session requests and the conversation requests are rejected.