If you are accessing existing data in a relational database, you need to know how to declare your data so that it will match the database fields.
If your COBOL code isn't written yet, you should follow the guidelines given in the topics for your specific RDBMS.
If your COBOL application already exists, you can make necessary adjustments by adding directives to your code. Directives are comments that guide the creation of the data dictionaries. The dictionaries in turn help map the COBOL fields to their equivalent database fields. Directives are described in the Using Directives section.