A quoted string containing full or partial information needed to
    access a database.

    For an Oracle Rdb database, an attach specification contains the
    file specification of the .rdb file.

    When you use the FILENAME argument, any changes you make to
    database definitions are entered only to the database system
    file, not to the repository. If you specify FILENAME, your
    application attaches to the database with that file name at run
    time.

    If you specify FILENAME:

    -  During compilation, your application attaches to the specified
       database and reads metadata from the database definitions.

    -  At run time, your application attaches to the specified
       database.

    For information regarding node-spec and file-spec, see Oracle Rdb
    Attach Specifications.