Formatted screen input

CICS® normally reads a 3270 screen with a read modified command. CICS provides an option, BUFFER, for the terminal control RECEIVE command, with which you can capture the entire contents of a 3270 screen.

The data transmitted depends on what the operator did to cause transmission:

The ENTER key or a function key
CLEAR, CNCL or a PA key (the “short read” keys)
Field selection: cursor select, light pen detect or a trigger field

You can tell which event occurred, if you need to know; how to do this is explained in Using the attention identifier. You can also find more detail on 3270 input operations in Input from a 3270 terminal.

The short read keys transmit only the attention identifier (the identity of the key itself). No field data comes in, and there is nothing to map. For this reason, short read keys can cause the MAPFAIL condition, as explained in MAPFAIL and other exception conditions. Field selection features transmit field data, but in most cases not the same data as the ENTER and function keys, which we describe in the paragraphs that follow. See Support for special hardware for the exceptions if you plan to use these features.

Most applications are designed for transmission by the ENTER key or a function key. When one of these is used to transmit, all of the fields on the screen that have been modified, and only those fields, are transmitted.