MAPONLY or DATAONLY map display issue

BMS map problems — MAPFAIL, blank fields, layout mismatches — come from the map definition disagreeing with the program.

What it means

• MAPFAIL means no data was entered (all fields empty or unmodified).
• Blank fields often mean the symbolic map layout does not match the physical map.

Common causes

• User pressed ENTER without entering data (MAPFAIL is normal here).
• Symbolic map copybook out of sync with the mapset.
• Wrong map name in the RECEIVE.
• Field attributes preventing input.

How to diagnose

• Handle MAPFAIL explicitly — it is often not an error.
• Compare the symbolic map copybook with the assembled mapset.
• Check the map name in RECEIVE MAP.

How to fix it

• Treat MAPFAIL as "no input" business logic.
• Regenerate the symbolic map from the current mapset.
• Correct the map name.

Example: Handle MAPFAIL as a normal case

MAPFAIL usually means empty input, not a bug.

Interview tip

• Q: How would you troubleshoot a MAPONLY or DATAONLY map display issue in production?
• A: I would first rule out normal MAPFAIL, then compare the symbolic map with the assembled mapset and fix the mismatch.

Prevention checklist

• Generate symbolic maps from the mapset in the build.
• Handle MAPFAIL in every RECEIVE.