The XCF Server stub routine gets control when you invoke IXCSRVR to start a server. The purpose of the stub is to wait for client requests to arrive and then call the user's server exit routine to process requests as they arrive.

After selecting a server instance to process the request, XCF constructs the server exit parameter list (SXPL) and calls the server exit routine to process the request. The SXPL provides information about the client request and identifies the storage location where the content of the client request message was stored.

XCF puts the address of the parameter list in register 1 and calls the server exit routine. Register R13 contains the same value as when the IXCSRVR macro was invoked to start the server (including AR13 if invoked in AR mode). The server exit routine receives control in the same environment as that of the IXCSRVR macro when it was invoked to start the server, except that it is now running under XCF recovery. In particular, the server exit routine receives control in the same addressing mode, the same ASC mode, with the same PSW key, and in the same state (supervisor or problem) as when the IXCSRVR macro was invoked to start the server.

For more information on coding a server exit routine, see Coding a server exit routine.