The NULL XFD directive handles NULL values in numeric tables by comparing non-key field values when performing read and write actions on the database to determine and perform appropriate actions.
Specify the NULL XFD directive on individual numeric fields within the COBOL FD.
During a write to the database, this directive compares the value of the COBOL numeric field against its own set literal value. If the values are equal, it writes a NULL value to the database.
During a read of the database, if a NULL value is returned, this directive places its own set literal value into the COBOL numeric field before returning to the COBOL program.