There are several elements of COBOL that require special handling when data dictionaries are built. These include multiple record definitions, REDEFINES, FILLER, and OCCURS.
Databases generally do not support the notion of multiple definitions for the same column. (In a similar sense, when you are editing a data file, it makes sense to see and change only one view of the data, rather than multiple views.) As the following paragraphs explain, whenever a COBOL program gives more than one definition for the same data, the compiler makes a choice about which definition to use in the data dictionary. Then it disregards the rest.