Using the display screen to share data

You can also store data between pseudoconversational transactions from a 3270 display terminal on the display screen itself. For example, if users make errors in data that they are asked to enter on a screen, the transaction processing the input usually points out the errors on the screen (with highlights or messages), sets the next transaction identifier to point to itself (so that it processes the corrected input), 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 very easy to code, but it is not very secure. You are not recommended to save screens that contain large amounts of data as errors may 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. You can avoid this by defining the CLEAR key to mean CANCEL or QUIT, if this is appropriate for the application concerned.

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

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