A service requester pipeline

In a service requester pipeline, an application program creates a request, which is passed through a pipeline to the service provider. The response from the service provider is returned to the application program through the same pipeline.

When CICS® is in the role of service requester, it performs the following operations:
  1. Use data provided by the application program to construct a request.
  2. Send the request to the service provider.
  3. Receive a response from the service provider.
  4. Examine the response, and extract the contents that are relevant to the original application program.
  5. Return control to the application program.
Figure 1 illustrates a pipeline of three message handlers in a service requester setting:
Figure 1. A service requester pipeline
CICS Transaction Server is connected to a service provider. The application links to the pipeline, which contains three handlers: handler 1, handler 2 and handler 3 are non-terminal handlers.
  1. An application program creates a request.
  2. Message handler 1 receives the request from the application program, 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).
  3. Message handler 2 receives the request from handler 1, performs some processing, and passes the request to handler 3.
  4. Message handler 3 receives the request from handler 2, performs some processing, and passes the request to the service provider.
  5. Message handler 3 receives the response from the service provider, performs some processing, and passes it to handler 2.
  6. Message handler 2 receives the response from handler 3, performs some processing, and passes it to handler 1.
  7. Message handler 1 receives the response from handler 2, performs some processing, and returns the response to the application program.