Designing and Programming CICS Applications

Part V. The 3270 Interface

The limitations of 3270 devices are usually compensated for by designing and building the system for high performance, with typical response times for a query usually being less that half a second. From the early 1970s, 3270 devices brought transaction processing to the end user. The design point was to produce useful data to the end user in less than a second over a network which had a bandwidth that would be considered to be abnormally narrow today. If the end users were paid by the number of transactions they finish, a terse layout is the right design and implementation for this interaction with their company system.

There are two reasons why you may have a need to understand the information in this part:

• Because you are writing a new 3270 application. Even in this case, the CICS facilities hide most of the technical details of the hardware from your program.

• Because there is an existing 3270 application that you need to invoke from your own program. You will be issuing API calls that the existing program interprets as user keystrokes. Again, there are CICS and other facilities that hide the technical details.

This Part provides detailed information about the 3270 interface for our sample CICS application and contains Chapter 10, and Chapter 11.