Each of the services has an installation exit. Each installation exit for a service has two exit points:

• The Preprocessing exit point. This exit point occurs after an application program calls a service, but before the service starts processing. For example, you can use this exit point to check or change the parameters that the application passes on the call, or to end the call. You can also perform additional security checks.
• The Postprocessing exit point. This exit point occurs after the service has finished processing, but before the service returns control to the application program. For example, you can use this exit point to check and change the return code from the service or perform cleanup processing.