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# Chapter 1 . Introducing BEA Connect TCP for CICS

## Feature Overview

Connect TCP for CICS is a gateway connectivity feature that makes it possible for non-transactional tasks within BEA TUXEDO regions to access services provided by CICS application programs and vice-versa. A BEA TUXEDO region, or administrative domain, is a single computer or network of computers that shares a single BEA TUXEDO configuration.

Connect TCP for CICS is designed to provide transparent CICS program access from within a BEA TUXEDO domain and BEA TUXEDO access from within a CICS region.

## Connect TCP for CICS Architecture

Connect TCP for CICS is composed of three CICS programs running within the CICS region. It uses the Sockets Interface and Sockets for CICS Listener that is shipped with the IBM TCP/IP for CICS/ESA Sockets Interface. There are two different processing scenarios to consider:

- Requests that originate in a remote BEA TUXEDO domain and request services offered by CICS

- Requests that originate in a CICS region and request services offered by a remote BEA TUXEDO domain

## Connect TCP for CICS Components

There are three programs used in processing remotely and locally initiated requests. Additionally, there is an on-line CICS administrative tool for configuring and maintaining the BEA Connect TCP/CICS Gateway.

### The Connect TCP for CICS Handler

A Connect TCP Handler is a CICS program that communicates with the Connect TPS Requester over TCP/IP; specifically, the Handler communicates BEA TUXEDO requests to a CICS region. A Handler is started automatically within a CICS region when a Requester within BEA TUXEDO issues the first service request destined for that CICS region.

The Handler is responsible for accepting a connection request, taking control of the sockets connection, and continuing communication with the Requester in the BEA TUXEDO domain for the life of the sockets connection. The Handler is also responsible for processing service requests originating from the Connect TPS Requester. The Handler executes the target User Application, waits for the application to return data, transmits that data back to the Requester, then waits for the Requester to send another service request.

### The Connect TCP for CICS Pre-requester

The Pre-Requestor program is used as an interface between your CICS client program and the Connect TCP for CICS Requester. The CICS Requester, which is described in the next section, is the program that talks with the remote BEA TUXEDO region. From your CICS client program you call the Pre-requester by issuing an EXEC CICS LINK.

### The Connect TCP for CICS Requester

The Requester program is responsible for making and maintaining the sockets connection with the remote BEA TUXEDO region. After receiving request information from the Pre-requester, the Requester sends that information to BEA TUXEDO. The Requester then receives any response data returned by BEA and sends it back to the Pre-requester, which in turn gives the information back to the client program that had called it.

### IBM TCP/IP Sockets Interface

The sockets interface must be enabled before Connect TCP for CICS can communicate over TCP/IP. This is true for any CICS program which uses the sockets API. The IBM TCP/IP Sockets Interface is not supplied by BEA Systems, Inc. You can purchase it directly from IBM. The supplied transaction CSKE that accompanies the IBM TCP/IP Sockets for CICS product is used to enable the sockets interface under CICS. Complete documentation is provided with the product.

Note: You must configure the TCP.PROFILE parameter with a maximum buffer size of at least 10,000.

#### Using Other Supported TCP/IP Sockets Products

This document refers to the IBM TCP/IP sockets interface product. If you are using another supported TCP/IP product (such as Interlink TCPaccess) consult that product's documentation for equivalent components.

### IBM User Maintained Tables (UMT)

The Connection file, BEAVCON, defaults to a user maintained table (UMT). If you choose to change this file to a VSAM file you must add the transaction BDWN to PLTSI for CICS. This transaction's primary function is to shut down all the active Requesters, but one of its secondary functions is to remove all the entries from the Connection file. The Connection file must be empty before any activity.

### IBM TCP/IP Sockets for CICS Supplied Listener

The IBM TCP/IP Sockets for CICS Supplied Listener is responsible for capturing the initial connection request and passing that request along to the Connect TCP for CICS Handler. It is a piece of the IBM TCP/IP Sockets for CICS product which you must purchase directly from IBM. The listener should be installed and configured as outlined in the manual shipped with the product.

## Processing Scenarios

This section describes the BEA Connect TCP for CICS processing scenarios.

### Requests from within a BEA TUXEDO Domain

Because of the way BEA TUXEDO maps services to servers, service requests from remote BEA TUXEDO regions to Connect TCP are transparent to the user, the BEA TUXEDO developer, and the CICS programmer.

As Figure 1-1 shows, Connect TCP for CICS extends this transparent access by routing BEA TUXEDO's requests for CICS program services through TCP/IP network software.

> Figure 1-1 Connect TCP for CICS to BEA Connect MVS/CICS Routing

As Figure 1-1 suggests, Connect TCP for CICS fits between the CICS User Application and TCP/IP.

When BEA TUXEDO client programs send requests to remote systems (in this case, CICS) Connect TCP for BEA TUXEDO transforms those requests into messages formatted appropriately for transmission to the remote system. Also, when remote systems respond, Connect TCP for BEA TUXEDO transforms these responses into replies that local client programs can process.

Connect TCP for CICS is implemented as an ordinary CICS program which communicates with the Sockets Interface. It accepts connection requests from Connect TCP and returns standard replies.

A maximum of 50 simultaneous socket connections can exist between one Connect MVS/CICS Gateway (a set of Connect Handlers within a single CICS region) and all remote Connect TPS Requesters. Each socket connection is established automatically when a new Connect TPS Requester in the BEA TUXEDO domain establishes communication with the Connect TCP for CICS Gateway.

### Requests from within CICS

The mechanism used to send requests initiated from a CICS program to a remote BEA TUXEDO domain is invisible to the user and significantly abstracted from the CICS programmer. Your company's CICS program issues an EXEC CICS LINK command to the BEA Connect gateway. In the data passed with the EXEC CICS LINK command, the programmer supplies the name of the service and the data to be used as input to that service. When the EXEC CICS LINK command returns, the reply to the request is placed in that same data area. If there was a problem satisfying the service request, meaningful return codes are sent back.

> Figure 1-2 BEA Connect Client Gateway Configuration

Figure 1-2 shows the configuration of the BEA Connect client gateway. A client program (your CICS program) issues an EXEC CICS LINK command to the Pre-requester. The Pre-requester verifies that the service name is valid and identifies the Requester to which it should it should pass the request. The Pre-requester starts a different Requester for each configured remote endpoint. The Requester then sends the request to the remote BEA TUXEDO domain and waits for a response. Once the response is returned, the Requester notifies the Pre-requester and hands the response to the Pre-requester, who then returns the response to the client program.

## Getting Started with BEA Connect TCP for CICS

The following list describes all the tasks you must perform before you can begin using BEA Connect TCP for CICS.

- Ensure that MVS TCP/IP is installed and configured

- Ensure that the Sockets for CICS interface and supplied listener are installed and configured. The listener product comes with the Sockets for CICS interface

- From the MVS TCP/IP administrator, find out at which port and address your supplied listener should listen. Give this information to the BEA TUXEDO administrator so that the remote BEA Connect TPS component knows where to find the CICS TCP/IP listener

- Find out on which port(s) BEA Connect TPS will be listening. You will need this information when you begin setting up services

- Follow the installation instructions for BEA Connect TCP given in Chapter 3, "Installing BEA Connect TCP for CICS"

- Using the administration tool (described in Chapter 5, "Administering BEA Connect TCP for CICS") define the services and remote endpoints for use by BEA Connect TCP. The best way to approach this is to talk to the BEA TUXEDO administrator and choose one service only. Attempting to set up all the services at once would be a complex task, but after you learn how to set up one service, you should have no difficulty setting up the others

- Add an EXEC LINK statement to one of your CICS programs and set up the data area as described in Chapter 2, "Understanding How BEA Connect TCP for CICS Works" of this manual

- Talk with your BEA TUXEDO administrator about service names (what you will call a service and what BEA TUXEDO calls it) and the layout of data each service expects to make sure there will be no consistency problems

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