Writing the Link3270 client

To design and write a client program to run an existing CICS® 3270 transaction using the Link3270 bridge you need to:
  1. select a suitable bridge scenario to decide where code needs to be written
  2. analyze the application to understand the business data that flows between the 3270 and the application, so that you can replace it with messages
  3. decide whether you can use the simplified single transaction mode interface or whether you need to use the full session mode interface
  4. Write you client program using the selected scenario and transaction mode, using Link3270 messages to communicate with Link3270.
Link3270 has two modes of operation:
Single transaction mode
This is a 'one-shot' type of request. A single transaction is run, and a single response message returned. The bridge facility is allocated automatically by CICS and deleted at the end of the transaction. This mode is appropriate for inquiry type applications.
Session mode
This mode is appropriate for sequences of transactions where state data is maintained between transactions. In this mode, the client program can request:
  • allocation of a bridge facility
  • running of a transaction
  • sending of continuation responses
  • recovery from communication failure
  • deletion of the bridge facility

Your client program manages the sequence of requests and the creation and deletion of the bridge facility. Note that this is different from the implementation of the START bridge, where the bridge facility is created dynamically.