Designing and Programming CICS Applications

Chapter 4. Designing the Business Logic

In this chapter:

• Understanding What COBOL Components Need to Do

• Incorporating CICS Design Guidelines

• Handling Data

• Designing the Individual Functions

• Mapping the Functions to CICS Programs

• Looking at the Business Logic Programs

The specification outline for the COBOL business logic component for the sample application is a simple one—to provide a program to perform create, read, update, delete, and browse operations on the customer account file.

The design phase for the component specifies in detail:

• The interfaces to the component

• Any errors the component may encounter and report

• Usage constraints, such as the need to call the read operation before calling the update operation

It is important to note before starting to design and develop the component that the simple and incomplete specification above could be implemented in many ways, altering the balance of responsibilities and affecting the ease of development and debugging of the total application. In the real world, the final specification only evolves after several meetings involving the architect and the component developers, and a number of redesigns. As they work through the sample to get it right first time, consultation with the users of the application is critical to ensure the correct design decisions. During the design stage, you should include the following steps:

• Determine what the COBOL component should do

• Incorporate CICS design guidelines

• Determine data handling

• Design the individual functions ...