You can use the External Call Interface (ECI), External CICS® Interface
(EXCI), or Distributed Program Link (DPL), potentially via CICS Transaction
Gateway (CTG) or a distributed version of CICS, to invoke an adapter service. When
you use a CICS-supplied interface, the request can only be processed in synchronous
mode.
- Select the interface that is appropriate for your service requester.
- If you want to use CTG to invoke the adapter service, use the
ECI interface. However, if CTG is installed on z/OS®, the EXCI interface is actually used.
- If you want to use DPL, use the EXEC CICS LINK command
to link from the service requester to the DPL stub program with a request
message. If you opt for DPL, you can use a channel and containers
to pass the request message, rather than a COMMAREA.
- Decide what data conversion is required. It might be
necessary to perform data conversion in the CICS Service Flow Runtime routing
region, using a customized version of the standard CICS conversion table DFHCNV. For details,
see Data conversion.
- Decide how you want to send the request message from
the service requester to invoke the adapter service. The service
requester can send the message in a COMMAREA, or if you are using DPL a set
of containers.
The service requester then waits for a response if
required.
- When the adapter service has completed its processing of the request
message, the DPL stub program passes the response message back to the service
requester. The CICS-supplied interface requires a response, but
the request message might not require an application reply.