Chapter 1   Basic Connector Concepts


This chapter describes the three-tiered web-based computing model. It also summarizes the main functions of the enterprise CICSs which enable the communication between the web-based end user and a remote EIS data source.

The chapter discusses the following:

• Three-Tier Application Model

• About UIF

• Architecture of the CICS Connector

• Enterprise Connector Tools for CICS

Three-Tier Application Model

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iPlanet Enterprise Connectors are and integral part of the middleware between enterprise data sources and the clients that access those data sources. The machine and software involved are divided into three tiers:

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

• a server tier represented by a web server such as iPlanet Web Server and an application server which runs the business code such as iPlanet Application Server.

• a data tier, represented by relational databases or other backend data sources such as Oracle or CICS.

The connectors serve as an essential link allowing the server tier to communicate with the data tier, as shown in the following illustration.

Figure 1-1    Three-tier web-based computer model

In addition to the enterprise connector, communication between the application server and the backend EIS is facilitated by the Unified Integration Framework (UIF) application programming interfaces (API). This layer of functionality resides as an added layer to the iPlanet Application Server and enables data communication with diverse backend Enterprise Information Systems (EIS) to be implemented in a seamless and uniform manner.

About UIF

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The iPlanet Application Server Enterprise Connector for CICS uses the UIF module of the iPlanet Application Server to communicate with CICS and a number of other EIS data sources. PeopleSoft, SAP R/3, and Tuxedo are also supported by the UIF set of APIs with more planned for the future, as shown in the following illustration.

Figure 1-2    The Unified Integration Framework

The UIF is a toolkit that enables development of application server extensions that integrate with new, web-based enterprise applications and systems, client-server applications, and third-party Internet solutions. These extensions provide a consistent access layer to disparate back-end systems, dramatically reducing development effort. The framework provides support for features such as object-pooling, distributed state and session management, template streaming, and multi-threading enables high-performance, fault-tolerant integration that can scale to tens-of-thousands of users. Corporate IT developers, application vendors, and system integrators can easily build server extensions to iPlanet Application Server in Java or C/C++.

The UIF provides generic function like data pooling and user mapping for the enterprise connectors to use. An iPlanet Application Server Enterprise Connector for CICS takes generic calls into this UIF-provided functionality and translates it into functions that are specific to CICS.

A generic data repository is also provided by the UIF, which is used to hold metadata parameters and other information about the backend system. For example, this metadata often describes the physical connection between systems, the data that is available, and the methods you can use to process data.

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

Architecture of the CICS Connector

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Besides the UIF module that provides backend-independent core services, the iPlanet Application Server Enterprise Connector for CICS includes an implementation of the repository which you use to mine for data and specific data access services that can be used to drive the connector.

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

The iPlanet Application Server Enterprise Connector for CICS stores data that defines the services available to an iPlanet Application Server servlet or EJB from a CICS system in the repository. Repository data includes two types of metadata definitions:

• Connector types
  These define CICS-specific characteristics, including the kinds of operations that are available (function-object types) and the kinds of logical connections that are supported (service-provider types).

• Data sources
  These define the logical data source that specifies data and business functions available on a specific backend system.

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

Connector-to-CICS Architecture

One or more iPlanet Application Server for CICS-enabled servers (iPlanet Application Servers with iPlanet Application Server for CICS installed) can communicate with backend CICS regions. The following diagram shows the overview of the components between the server and the MVS machine that hosts CICS over APPC:

SRVXLINK is the CICS program which calls to the user's CICS server program. The default transaction name of SRVXLINK is SRVX.

The conversation with the CICS transactions is either persistent or non-persistent. In order to achieve scaling, the connections to the SRVXLINK are direct in iPlanet Application Server for CICS and can be re-used by many other users. The connection to SRVXLINK should be closed after each transaction, that is, the value of a request should have a SendAndEnd. 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 SRVXLINK. The SRVXLINK then calls to the user's programs.

Connector-to-CICS Program Control

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.

• SRVRSRPC, which includes an connector-to-CICS communications API that allows you to explicitly transfer data between your CICS program and iPlanet Application Server for CICS.

• CICS-to-Connector communications software, which is used internally to make the connection from the connector to CICS, via the Relay (over TCP/IP) or SRVXLINK (over APPC).

• Relay (TCP/IP only).

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

If your program does not follow DPL guidelines, you must either modify the program to follow the guidelines, in which case you can use SRVXLINK, or you can modify your program to use the SRVRSRPC module. If you must modify your program, making it DPL-compliant would be a less proprietary solution than using SRVRSRPC. The SRVRSRPC module and the Connector-to-CICS communications API are provided for cases in which modifying your program to follow DPL guidelines is more difficult than implementing SRVRSRPC-based access to iPlanet Application Server for CICS from within your program. For more information about SRVRSRPC and the Connector-to-CICS communications API, see Chapter 4 "Server-Side API Communication.

Enterprise Connector Tools for CICS

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A set of tools are used for data mining, user mapping, and general configuration with iPlanet Application Server Enterprise Connector for CICS include:

• Repository Browser

• CICS Management Console

• CICS Data Mining Tool

Repository Browser

The Repository Browser allows you to view the contents of the repository and to import and export XML files. A typical Repository Browser is shown below:

Figure 1-3    Repository Browser

You can:

• import nodes and subtrees

• export XML files with all subtrees under a node

• delete nodes

• import root nodes

CICS Management Console

The CICS Repository Management Console allows you to browse or change the CICS configuration, and to monitor the CICS system status. The SAP Management Console is shown below:

Figure 1-4    CICS Management Console

CICS can retrieve XML files from remote computers and save them into the repository.

You can also:

• convert data to XML

• create new data sources

• edit existing data sources

CICS Data Mining Tool

The CICS Mining Tool, which is part of the Management Console, allows you to determine the available transactions on the CICS system and to load this metadata into the repository.

The elements of the data-mining are shown in the following illustration.

Figure 1-5    Elements of the Data Mining

The user selects the COBOL files, mines these files, converts them to XML, and then loads them into the repository.