The application designer may define ID fields to be persistent. This usually occurs when the designer does not anticipate the IDs changing between cases within the data file, such as for geographic IDs. The operator will enter values for the first case, and then the system will use those values for the IDs of subsequent cases.
However, if the operator needs to change an ID, they can do so by successive presses of the F7 key, which will back the operator up through the ID fields.
Persistent fields are shown as light gray boxes on the form.