Session outage notification

Stages of session termination gives an overview of certain events that can lead to session termination. Usually, an application program includes SCIP, NSEXIT, and LOSTERM exit routines. These routines are scheduled to notify the application program of various types of session outages and related events. Exit routines related to session establishment and termination describes these exit routines. Table 1 provides a more detailed list of session outage notification (SON) reasons.

If the relevant exit routines are not coded in the application program, the program might not be informed of certain key events in a timely manner (if at all). Thus, the exit routines should be coded.

Note: Normally, when an outage occurs for a session, outstanding RPL-based operations for the session are posted complete with appropriate feedback information; this is not always possible if the outage is because of a VTAM® abnormal termination. For a given session outage, the order in which the RPL exit routine and the SCIP, NSEXIT, or LOSTERM exit routines are scheduled is unpredictable.

The exit routine chosen depends upon:

The type of session outage event
Whether the application program is the PLU or the SLU in the session
The availability of the various exit routines

Note: An exit routine is available if it is specified in an EXLST for the application program. In some cases, if the exit routine normally scheduled for an event is not available, an alternate exit routine schedules. See Table 1 for information about session outage notification and Table 1 for a more detailed list of session outage notification reason codes. For information on exit routines and their availability, see SCIP exit routine, NSEXIT exit routine, and LOSTERM exit routine.

It is possible for one session outage to generate multiple session outage notification signals to an LU (along different paths through the network) for the same disrupted session. For example, CLEANUP and UNBIND can both be sent to an LU.