What are advantages of I/O Module?

• Centralization of validation rules logic. Dictionary and file level validation code is compiled into the I/O module and not repeated in every process that uses the file. Thus the validation rules can be changed without the need to recompile every process that accesses the file.
• True data independence. A file can be changed without the need to recompile every process that uses the file. This includes changing the definition of existing fields in the file as well as adding new fields to the file.
• Faster compiles of user defined processes because there is no direct reference to the external database definition.
• Support for virtual fields. These fields, derived from "real" fields in the file, appear as if they are in the database file, even though they don't really exist.