Restrictions on Validity Checking for Display Files

Validity checking keywords (CHECK, COMP, RANGE, and VALUES) can be specified with the DUP keyword. However, they have no effect if the Dup key has been pressed.

If another field in the record format fails validity checking, the OS/400 program tries to read the display again. Whether or not the work station user keys over the DUP characters or presses the Dup key again, the DUP response indicator is still returned to your program in the on condition.