The following example shows how to define an indexed file for the
       domain PAYABLES using the field NAME as the primary key and TYPE
       as the alternate key, and allowing no changes to the alternate
       key:

       DTR> DEFINE FILE FOR PHONES KEY=NAME(DUP), KEY=TYPE(NO CHANGE)
       DTR>

       The following example defines a sequential file for the domain
       FAMILIES:

       DTR> DEFINE FILE FOR FAMILIES
       DTR>

       The following example shows how to define a new indexed file for
       the domain YACHTS using the group field TYPE as the primary key,
       allowing duplicate values for this key. This command replaces the
       previous data file for YACHT.

       DTR> DEFINE FILE FOR YACHTS SUPERSEDE, KEY=TYPE (DUP)
       DTR>

       The following example defines a new file for the YACHTS domain
       using the specifications included in YACHTS.FDL, a file created
       outside of DEC DATATRIEVE:

       DTR> DEFINE FILE FOR YACHTS USING YACHTS.FDL
       DTR>