5250 error 0019: Dup or Field Mark key not allowed in field

What it means

The Dup key comes from high-volume data entry. An operator keying a stack of forms presses Dup in a field to say the value is the same as on the last record, instead of typing it again. The display station fills the field from the cursor to the end with a special duplication character, hex 1C, and sends the screen as usual. IBM's DDS reference is clear that the program does the actual copying. The display station only marks the field.

A field takes Dup only if the display file allows it, with the DUP keyword on that field. Press Dup anywhere else and the display station refuses the key, locks the keyboard and shows 0019. The same code covers the Field Mark key on keyboards that have one.

Few people press Dup on purpose today. On a PC the key is usually mapped to a key combination in the emulator, and 0019 often means that combination was pressed by accident.

Common causes

• You pressed Dup expecting the field to repeat its last value, but the program allows Dup only on some fields, and this isn't one of them.
• You pressed the key or combination your emulator maps to Dup or Field Mark without meaning to.
• The DUP keyword on the field is conditioned by an option indicator, and the program left that indicator off for this screen.

How to find the problem

1. Check what key you pressed. Your emulator's keyboard map shows which key sends Dup and which sends Field Mark.
2. Press Help while 0019 is on the error line to see the system's text for the error.
3. In the display file source, look for DUP on the fields where Dup should work. A response indicator in the keyword, such as DUP(16), tells the program that Dup was pressed.

How to fix it

• Press Reset (also called Error Reset) to free the keyboard. In many PC emulators Reset is the left Ctrl key by default. Then type the value in full.
• If you pressed Dup by accident, check the keyboard map and move Dup to a key you are less likely to hit.
• For programmers, to allow Dup on a field, add the DUP keyword with a response indicator and recreate the display file with CRTDSPF. Then write the code that copies the previous value when the indicator is on. IBM's DDS example keeps the last value in a hidden field for this.
• For programmers, validate duplicated values in the program. IBM's reference says CHECK, COMP, RANGE and VALUES have no effect when Dup was pressed. For a numeric field, the hex 1C characters aren't returned to the program, so test the indicator rather than the field value.

Technical reviewer: Albert Joseph, WND Software.

Last reviewed 2026-10-18 by the WND Software team. Written in our own words. For the full reference, check IBM’s 3270 or 5250 display documentation.