Developing services in the service routine environment

The purpose of an application service routine environment is to allow the development, using z/OS® XL C, of services that can be developed, tested, and packaged independently of their intended users. You can:

Isolate the service code from its user
Specify and enforce a clearly defined Application Programming Interface (API) between the user (another application program) and the service routine
Share server code among more than one (perhaps different) user applications simultaneously
Enhance or maintain the service routine code with no disruption to its various user applications

In this environment, a service application is developed as a C main() function together with any functions it may call, and packaged as a complete program. This program, if it is reentrant, can be freely installed in the ELPA and shared by all of its users.

To provide the service to a user application, the developer of the service must offer small assembler language stub routines that are link-edited with the user code. These stub routines use services provided by the System Programming Facilities to load or locate the server code and pass messages to it for execution. Examples of these stub routines are shown in Constructing user-server stub routines.