Identifies the database root file associated with the database.
    If you specify a repository path name, the path name indirectly
    specifies the database root file. The ALTER DATABASE statement
    does not change any definitions in the repository, so there is no
    difference in the effect of the PATHNAME and FILENAME arguments.

    If you specify PATHNAME, SQL does not use the repository's fully
    qualified name. Instead, SQL uses the name stored as the user-
    supplied name in the repository. In the following example, SQL
    uses the name TEST as the file name, not DB$DISK:[DBDIR]TEST.RDB.
    As a result, the database root file must be located in your
    present working directory or the database name must be a logical
    name when you use the PATHNAME clause.

    $ REPOSITORY OPERATOR
       .
       .
       .
    CDO> show database/full test
    Definition of database  TEST
    |   database uses RDB database TEST
    |   database in file TEST
    |   |   fully qualified file DB$DISK:[DBDIR]TEST.RDB;
    |   |   user-specified file DB$DISK:[DBDIR]test.rdb

    If the database referred to in the PATHNAME or FILENAME argument
    has been attached, the ALTER DATABASE statement will fail with a
    file access conflict error.