COBOL data (except key data) that is illegal by database standards is stored in the database as null unless you specifically override this default. (Use the ACUFH configuration file variable 4GL_ILLEGAL_DATA to override.)
The following COBOL data usages are considered illegal by the database:
| Illegal Values | |
| USAGE DISPLAY numbers | LOW-VALUES , HIGH-VALUES, and SPACES |
| COMP-2 numbers | HIGH-VALUES and SPACES |
| COMP-3 numbers | HIGH-VALUES |
All other numeric types fit one of the preceding cases (depending on their internal storage format)
| DATE fields | The value "zero" and any other illegal conditions as defined by the date's USAGE type (see above) |
| text fields | LOW-VALUES |
BINARY numbers are always legal, and all values are legal in BINARY text fields.