Sending and receiving data

When a transaction is running on CICS®, data is passed between CICS and the user application.

This might be data produced by the transaction or one or more messages from the CICS server, for example terminal error messages. If the data is in the form of BMS map data, CICS also supplies the map name and map set name. If the map is to be returned to CICS for further processing, the user application must also return the map name and map set name.

Some programming languages have APIs that provide functions to help process the data stream.

There are two different programming models for EPI-based applications:

The screen model allows the user application to handle the 3270 data based on the structure of the fields in the 3270 data stream. In some languages it is also possible to import BMS map data to help with this process.
With the 3270 model, the user application reads the 3270 data stream as a simple data record and is responsible for parsing the information that it contains.

The user application is responsible for presenting the data received. The application can present the data by emulating a 3270 terminal, or it might present a different view. For example:

A Windows application might use the Windows graphical user interface.