SQL> select object_type from dba_objects 
   2 where object_name='V$TEMPSEG_USAGE';

OBJECT_TYPE
------------------
SYNONYM

SQL> select * from dba_synonyms 
   2 where synonym_name='V$TEMPSEG_USAGE';

OWNER      SYNONYM_NAME    TABLE_OWNE TABLE_NAME        DB_LINK
---------- --------------- ---------- ----------------- ----------
PUBLIC     V$TEMPSEG_USAGE SYS        V_$SORT_USAGE

SQL> SELECT view_definition FROM v$fixed_view_definition
  2  WHERE view_name='GV$SORT_USAGE';

VIEW_DEFINITION
--------------------------------------------------------------------------------
select x$ktsso.inst_id, username, username, ktssoses, ktssosno, prev_sql_addr, p
rev_hash_value, ktssotsn, decode(ktssocnt, 0, 'PERMANENT', 1, 'TEMPORARY'), deco
de(ktssosegt, 1, 'SORT', 2, 'HASH', 3, 'DATA', 4, 'INDEX', 5, 'LOB_DATA', 6, 'LO
B_INDEX' , 'UNDEFINED'), ktssofno, ktssobno, ktssoexts, ktssoblks, ktssorfno fro
m x$ktsso, v$session where ktssoses = v$session.saddr and ktssosno = v$session.s
erial#

SELECT x$ktsso.inst_id, username, username, ktssoses, ktssosno, prev_sql_addr,
       prev_hash_value, ktssotsn,
       DECODE (ktssocnt, 0, 'PERMANENT', 1, 'TEMPORARY'),
       DECODE (ktssosegt,
               1, 'SORT',
               2, 'HASH',
               3, 'DATA',
               4, 'INDEX',
               5, 'LOB_DATA',
               6, 'LOB_INDEX',
               'UNDEFINED'
              ),
       ktssofno, ktssobno, ktssoexts, ktssoblks, ktssorfno
  FROM x$ktsso, v$session
 WHERE ktssoses = v$session.saddr AND ktssosno = v$session.serial#
/