Select Link3270 client scenarios

The following scenarios describe some common client environments.

They show how you can develop your client program to run in the most appropriate environment to make best use of existing skills and experience. These scenarios demonstrate tiered client applications that enable you to divide the logic to make best use of skills and experience. They use some common terms:
Business client
The business client is concerned only with the business data and its representation in the client end-user environment
bridge client
The bridge client builds the bridge messages and manages the communication with the bridge using the Link3270 interface. You can develop the more complex bridge client to run in CICS® , using CICS commands, and the business client portion can run in any environment that allows communication with the bridge client. The bridge client can be designed to be reusable.
  1. Host CICS Client

    In this scenario, shown in Figure 1 , the programmer has CICS skills and experience, so it is more appropriate to write the Link3270 interface code on CICS.

    You can separate the client logic into a business client, and a bridge client.

    The LINK and EXCI samples show how a client application can be separated in this way and how common logic can be shared in the bridge client. Note that a business client in another CICS region can use DPL to access the bridge client.

    Figure 1. Link3270 host CICS client scenario
    Diagram showing a business client running in CICS using the LINK interface; a business client running in z/OS using the EXCI interface; and a business client running on a remote workstation using ECI, to access an intermediate bridge client running in CICS that uses the LINK interface to the bridge. As described in the preceding text. The bridge router program then links to the driver task to start the target user transaction in a bridge environment.
  2. CICS Workstation Client

    In this scenario, shown in Figure 2 , where a CICS product is installed on the workstation ( such as CICS for Unix) then the client can be a CICS program using LINK to interface with Link3270, or with a host CICS bridge client. In the three tier model the writer of the bridge client needs to have CICS skills, but the business client programmer only needs skills on that platform.

    Figure 2. Link3270 CICS workstation client scenario
    Diagram showing a client running in a remote CICS workstation using DPL to access either 1)an intermediate host bridge client, that then uses LINK to drive the Link3270 bridge, or 2) links directly to the bridge. As described in the preceding text. The bridge router program then links to the driver task to start the target user transaction in a bridge environment
  3. Non - CICS Workstation Client

    In this scenario, shown in Figure 3 , the programmer has workstation skills and limited CICS experience. For the two tier scenario, the programmer must have some CICS experience to understand the messages (which involve EXEC CICS instructions).

    The client program executes on a remote workstation, using ECI to drive the user application. A single client program is written, combining the business logic in the client environment and the interface to Link3270.

    Figure 3. Link3270 non-CICS workstation client scenario
    Diagram showing a combined business/bridge client running in a remote workstation, using ECI to communicate directly with the bridge. As described in the preceding text. The bridge router program then links to the driver task to start the target user transaction in a bridge environment
  4. 3–tier Workstation client

    In this scenario, shown in Figure 4 , the workstation business client calls a bridge client in another environment, perhaps to utilize existing skills. For example, a Unix program could send a user-defined XML message to WebSphere® on z/OS® . A user-written bridge client application in WebSphere could then parse the XML message and convert it to a Link3270 message and use an EXCI LINK to call Link3270.

    Figure 4. Link3270 3–tier client scenario
    Diagram showing a business client running in a remote non-CICS workstation, sending an XML communication to an intermediate Websphere system ( running in a workstation or in z/OS where a bridge client uses a further appropriate communication method to access the bridge ( ECI or EXCI) . The bridge router program then links to the driver task to start the target user transaction in a bridge environment As described in the preceding text.