In a service provider pipeline, CICS® receives a request, which is passed
through a pipeline to the target application program. The response from the
application is returned to the service requester through the same pipeline.
When CICS is
in the role of service provider, it performs the following operations:
- Receive the request from the service requester.
- Examine the request, and extract the contents that are relevant to the
target application program.
- Invoke the application program, passing data extracted from the request.
- When the application program returns control, construct a response, using
data returned by the application program.
- Send a response to the service requester.
Figure 1 illustrates a pipeline
of three message handlers in a service provider setting:
Figure 1. A service provider pipeline
- CICS receives
a request from the service requester. It passes the request to message handler
1.
- Message handler 1 performs some processing, and passes the request to
handler 2 (To be precise, it returns control to CICS, which manages the pipeline. CICS then passes
control to the next message handler).
- Message handler 2 receives the request from handler 1, performs some processing,
and passes the request to handler 3.
- Message handler 3 is the terminal handler of the pipeline. It uses the
information in the request to invoke the application program. It then uses
the output from the application program to generate a response, which it passes
back to handler 2.
- Message handler 2 receives the response from handler 3, performs some
processing, and passes it to handler 1.
- Message handler 1 receives the response from handler 2, performs some
processing, and returns the response to the service requester.