Chapter 1   Overview


The iPlanet Application Server Enterprise Connector for CICS is used for building and delivering scalable applications that integrate the application server with legacy CICS applications. The iPlanet Application Server Enterprise Connector for CICS enables communication between an end user and a remote CICS Enterprise Information System (EIS). This chapter introduces the three-tier, web-based computing model and describes the basic connector concepts.

This chapter contains information about the following topics:

• Unified Integration Framework

• The Three-tier Application Model

• Architecture of the CICS Connector

• Enterprise Connector Tools for CICS

Unified Integration Framework

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The Unified Integration Framework (UIF) is an application programming framework that provides a single Application Programming Interface (API) to access different back-end systems. A connector is developed for each EIS to allow communication between the UIF API and the EIS, see Figure 1-1. The UIF API is the only API necessary to access the EIS.

Figure 1-1    CICS Integration

The UIF enables development of server extensions that integrate with legacy CICS applications and systems, client-server applications, and third-party Internet solutions. These extensions provide a consistent access layer to disparate EIS, dramatically reducing development effort. The framework provides support for features such as object pooling, distributed state, and session management.

A generic data repository is also part of the UIF, which is used to hold metadata parameters and other information about the EIS. For example, the metadata often describes the physical connection between systems, the data that is available, and methods you can use to process data. See Figure 1-2.

Figure 1-2    The Unified Integration Framework

Since EISs are implemented differently, the details for each EIS implementation differ.

UIF Services

The UIF is a component of the iPlanet Application Server. The iPlanet Application Server plays a prominent role in a three-tier application model. See the "The Three-tier Application Model" for a description. The UIF mediates between the iPlanet Application Server application and the EIS tier, namely the data sources and databases.

The UIF provides an API to access the following services:

• Runtime

• Data Object Services

• Repository and Metadata Services

Runtime

The UIF runtime services supply core services for resource management, thread management, communication and life cycle management, and exception management. The UIF runtime services understand and interpret metadata repository contents.

Data Object Services

The Data Object Services implements universal data representation common to all connectors. See Chapter 3 "Working With Data Objects" for description of data objects.

Repository and Metadata Services

The UIF repository and metadata services model a persistent information hierarchy that supports datatype definitions and inheritance. Italso manage the instances and reuse of data objects from datatype definitions.

The Three-tier Application Model

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The machine and software involved are divided into the following three tiers:

• Client Tier

• Server Tier

• EIS Tier

The connectors serve as an essential link allowing the server tier to communicate with the EIS tier, as shown in Figure 1-3. Communication between the application server and the EIS is facilitated by the UIF API. This layer of functionality resides as an added layer to the iPlanet Application Server and enables data communication with diverse EISs in a seamless and uniform manner.

Figure 1-3    Three-tier Web-based Computer Model

Client Tier

The client tier is represented as the user interface. Requests for data originate here, represented by web browsers or rich clients (such as a Java applet).

Server Tier

The server tier is represented by an application server and optionally a web server such as the iPlanet Web Server Enterprise Edition. The server tier houses the business logic (your application servlets and/or Enterprise Java Beans), and provides scalability, high availability load balancing, and integration with a variety of data sources.

EIS Tier

The EIS tier is represented by Enterprise Resource Planning (ERP) systems or other EIS data systems such as CICS.

Architecture of the CICS Connector

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The iPlanet Application Server Enterprise Connector for CICS allows you to build interactive web-based e-Business applications. Specifically, the iPlanet Application Server Enterprise Connector for CICS allows you to retrieve, display, and manipulate data within a CICS program that is initiated by an EJB or servlet.

The iPlanet Application Server Enterprise Connector for CICS stores data that defines the services available to a servlet or EJB from a CICS system in the repository. Repository data includes metadata definitions of Data Sources and Service Provider Types. These define general characteristics of CICS connector and configuration information about particular CICS systems.

A set of enterprise tools provides graphic user interfaces to help you manipulate the enterprise connector enabled CICS functionality.

Mainframe components

Installation of iPlanet Application Server for CICS on the mainframe includes the following modules:

• SRVXLINK, which automatically transfers data between iPlanet Application Server for CICS and a CICS program, passing data via the COMMAREA.

• Relay (TCP/IP only).

If your CICS program follows Distributed Program Link (DPL) guidelines, you do not need to modify your CICS program; you can use the SRVXLINK module, which automatically transfers data between CICS program (via the COMMAREA) and the iPlanet Application Server.

If your program does not follow DPL guidelines, you must modify the program to follow the DPL guidelines.

Connector-to-CICS Communication

The iPlanet Application Server Enterprise Connector for CICS communicates with the mainframe via TCP/IP or APPC.

The connector does not directly invoke user CICS transactions, rather the connector invokes the SRVX transaction (default) of the SRVXLINK program. The connector passes the user transaction name and any input parameters to SRVXLINK. SRVXLINK then invokes the user transaction, passing the input data via the COMMAREA.

The connection with the CICS back end is either persistent or non-persistent. Persistent connections are achieved by specifying a REQUEST field in the repository as SendLast. This causes a re-use of connections in the pool, and enable scaling to high transaction rates. This is the recommended mode of operation.

Non persistent connections are achieved by specifying a REQUEST field in the repository as SendAndEnd. This opens a new connection for each request. This mode of operation is suitable for infrequent (occasional) requests to CICS EIS.

Connector-to-CICS Architecture Over TCP/IP

iPlanet Application Server for CICS enabled servers can communicate with CICS regions. Figure 1-4 shows the interaction between the server and the MVS machine that hosts CICS over TCP/IP.

Figure 1-4    Connector-to-CICS Architecture Over TCP/IP

A Listener/Relay component resides on the OS/390 (MVS) operating system. It connects the iPlanet Application Server Enterprise Connector for CICS server, which communicates via TCP/IP, to the CICS system, which uses the SNA/APPC protocol (LU6.2).

The TCP/IP conversation with the application server is persistent, whereas the conversations with the CICS transactions can be nonpersistent. To achieve scalability, the connections to the relay are pooled in iPlanet Application Server Enterprise Connector for CICS and can be re-used by many other users. Each connection can be used to conduct many transactions with the CICS system. For example, when a user issues a request to run a new transaction in CICS, a connection is pulled from the pool and the request for a new transaction is forwarded to the relay. The relay then allocates a new conversation with CICS, which invokes a new transaction. For more information about pooling see the iPlanet Application Server Enterprise Connector for CICS Administrator's Guide.

Connector-to-CICS Architecture Over APPC

A SRVX transaction resides on OS/390 (MVS). It connects the iPlanet Application Server for CICS application server to the CICS server, which communicates via APPC to the CICS system.

One or more iPlanet Application Server for CICS enabled servers can communicate with CICS regions.

Figure 1-5 shows the interaction between the server and the MVS machine that hosts CICS over APPC.

Figure 1-5    Connector-to-CICS Architecture Over APPC:

Enterprise Connector Tools for CICS

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The Enterprise Connector Tools are as follows:

• Management Console - includes the User Mapping and Data Mining Tools
  • User Mapping - allows you to map user ID's for access into the EIS.

  • Data Mining Tool - includes capabilities of determining the available functions in the EIS, translating and reformatting data and loading data into the data repository.

• Repository Browser - allows you to browse data in the repository. You can view the available functions (input and output parameters) for the EIS. For developer's use of the Repository Browser see Chapter 2.

For more information about these tools, refer to the iPlanet Application Server Enterprise Connector for CICS Administrator's Guide.