Oracle: Deleting duplicates from a huge table

delete from t
where rowid in
 (select rid
    from (select rowid rid,
                 row_number() over (partition by KEY_FIELDS
                                      order by rowid) rn
            from t )
                where rn <> 1 );

reference :  http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1224636375004