Oracle Rdb uses the database handle to identify the particular
    database that is referenced by a database request. Note that the
    database handle should not be thought of as a program variable.
    The database handle provides context to any statement that uses
    the database handle. When your program accesses a single database
    you do not have to include database handles or scopes in the
    DATABASE statement. Unlike transaction handles and request
    handles, database handles do not have to be declared in your
    programs. The RDML preprocessor automatically generates the data
    declaration for the database handle.

    The database handle is used in several RDML statements and
    clauses to identify a database:

    o  DATABASE

    o  FINISH

    o  READY

    o  relation-clause of the record selection expression

    o  DEFINE_TYPE or DECLARE_VARIABLE (synonyms)

    o  BASED ON clause

    Oracle Rdb lets you have more than one database active at a given
    time. You can use the database handle to distinguish among these
    different databases in RDML statements.

    Both the default and named database handle are declared as GLOBAL by
    default.