A service function is the part of a server that satisfies a particular service request.

A server can handle different service requests by having a service function for each request. Requests identify the service function as well as the server. The server receives the request and passes control to the requested service function. For details, see Designing and Writing a Server.

Service functions can be related to the server in several ways: as subroutines of the server, as separate CSECTs, or as separate load modules.