COBOL does not have a concept that corresponds directly to SQL's NULL. The closest candidates in COBOL are data items that contain either SPACES or LOW-VALUES. In SQL, NULL is often used to indicate that the data is missing or not applicable.
To maintain the integrity of the source data and to ensure that any data written from your application back to the COBOL source is accurate, you must provide a representational mapping between COBOL's SPACES and LOW-VALUES and the corresponding SQL column values.
Use the NULL_ALPHA_WRITE variable to indicate how SQL NULLs in alphanumeric data should be translated into COBOL data. For data returned to the COBOL files (WRITEs), indicate whether the NULLs should be interpreted as SPACES or LOW-VALUES. Valid values are:
NULL_ALPHA_WRITE spaces NULL_ALPHA_WRITE low-values
By default, alphanumeric data is interpreted as SPACES on output to the COBOL source.