Application design

This chapter introduces some basic concepts to help you design CICS® applications. Changes are suggested that can improve performance and efficiency, but further guidance on programming for efficiency is provided in Design for performance.

The programming models implemented in CICS are inherited from those designed for 3270s, and exhibit many of the characteristics of conversational, terminal-oriented applications. There are basically three styles of programming model:

Once initiated, the applications typically use these and other methods of continuing and distributing themselves, for example, with pseudoconversations, RETURN IMMEDIATE or DTP. The main difference between these models is in the way that they maintain state ( for example, security), and hence state becomes an integral part of the application design. This presents the biggest problem when you attempt to convert to another application model.

A pseudoconversational model is mostly associated with terminal-initiated transactions and was developed as an efficient implementation of the conversational model. With increased use of 1-in and 1-out protocols such as HTTP, it is becoming necessary to add the pseudoconversational characteristic to the DPL or RPC model.

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