The SSI handles two types of requests: directed requests and broadcast requests.

Directed requests, which can be defined by the installation, are made to one named subsystem. For a directed request, the caller informs the named subsystem of an event, or asks the named subsystem for information. For example, you can access JES SYSOUT data sets with a directed request.

Figure 1 shows the processing for a directed request.

See SSI Function Codes Your Program Can Request for more information on the services available to your program using directed requests.

Figure 1. Processing for a directed request

Broadcast requests, which are defined by MVS™, provide the ability for subsystems to be informed when certain events occur in the system. Broadcast requests differ from directed requests in that the system allows multiple subsystems to be informed when an event occurs. The SSI gives control to each subsystem that is active and that has expressed an interest in being informed of the event. For example, your subsystem can be informed when a WTOR message is issued in order to automate a response to the WTOR.

Figure 2 shows the processing for a broadcast request.

See SSI Function Codes Your Subsystem Can Support for more information on the broadcast function codes your subsystem can support.

Figure 2. Processing for a broadcast request