The connection is created by an address space that provides a service that can be called by other programs. When the service is called, it needs to access notes in the note pad while running under the caller's work unit. Since the home address space of the work unit that calls the service will not normally be the server address space, the work unit is not deemed to be the connector and so would not qualify as a valid user of the connection. However, with a connection created for client usage, the work unit is permitted to access notes in the note pad when the work unit is running authorized. In practice, the service might receive control via a non-space switch PC.

Only an authorized program can create a connection for client usage. Furthermore, the work unit that uses the connection in this manner must be running authorized. When the connection is created, the home address space and primary address space of the requesting work unit must be the same space (the server address space). When the connection is used, there are no requirements with respect to primary and home address spaces.

Figure 1. Note pad connection with USAGE=CLIENT

In this style of use, the note pad is created by the server for its own purposes. It is intended for use by the server when running authorized in an arbitrary address space under a client work unit. The server should not normally give the caller direct access to the notes in the note pad. If it does so, the server is responsible for ensuring that the caller has the appropriate SAF authorization for such access. In cases where SAF authorization would be needed or the service routine needs to run unauthorized, it might be more appropriate for the server to create a connection for connector usage on behalf of the client (as described under Connector usage). Note that the connection would be deleted, and therefore no longer usable by clients, when the server address space terminates.

As was the case for a connection for server usage, a connection for connector usage could similarly be used to provide the service. The service routine would suspend the caller and process the notes asynchronously under a work unit running in the server address space that is deemed to be the connector. A connection for client usage permits synchronous access to the note pad and avoids the complexity and overhead of an asynchronous protocol.

Note that the USAGE=CLIENT connection can also be used by the server itself in any context where USAGE=CONNECTOR type accesses would be permitted. That is, had the connection been created with USAGE=CONNECTOR, work units originating from the server address space would have been permitted to use the connection. Any work unit that would have qualified for such usage qualifies as a valid user of the USAGE=CLIENT connection. The work unit need not be running authorized.