Using the display screen to share data

Data can be stored between pseudoconversational transactions from a 3270 display terminal on the display screen itself.

For example, errors made by users in data entry are highlighted (with highlights or messages) by the transaction processing the data. The next transaction identifier is then set to point to itself (so that it processes the corrected entry), and returns to CICS®.

The transaction has two ways of using the valid data. It can save it (for example, in COMMAREA), and pass it on for the next time it is run. In this case, the transaction must merge the changed data on the screen with the data from previous entries. Alternatively, it can save the data on the screen by not turning off the modified data tags of the keyed fields.

Saving the data on the screen is easy to code, but it is not secure. You are not recommended to save screens that contain large amounts of data as errors can occur because of the additional network traffic needed to resend the unchanged data. (This restriction does not apply to locally attached terminals.)

Secondly, if the user presses the CLEAR key, the screen data is lost, and the transaction must be able to recover from this. This can be avoided by defining the CLEAR key to mean CANCEL or QUIT, if appropriate for the application concerned.

Data other than keyed data can also be stored on the screen. This data can be protected from changes (except those caused by CLEAR) and can be nondisplay, if necessary.