SQL to check tempspace in oracle

SELECT b.Total_MB,
       b.Total_MB - round(a.used_blocks*8/1024) Current_Free_MB,
       round(used_blocks*8/1024) Current_Used_MB,
       round (max_used_blocks*8/1024) Max_used_MB
FROM v$sort_segment a,
  (SELECT round(sum(bytes)/1024/1024) Total_MB
   FROM dba_temp_files) b;