Oracle Temp Space Usage Related Queries

Based on Oracle 10g/11g

-- show summary temp tablespace usage
SELECT t.tablespace_name
      ,t.total_temp_mb
      ,u.used_temp_mb
      , (t.total_temp_mb - u.used_temp_mb) free_temp_mb
  FROM (SELECT   tf.tablespace_name
                ,   SUM (DECODE (tf.autoextensible
                                ,'YES', tf.maxbytes
                                ,'NO', BYTES
                                ))
                  / 1024
                  / 1024 total_temp_mb
            FROM dba_temp_files tf
        GROUP BY tf.tablespace_name) t
      , (SELECT   ss.tablespace_name
                 ,   SUM (ss.used_blocks)
                   * (SELECT ts.block_size
                        FROM dba_tablespaces ts
                       WHERE ts.CONTENTS = 'TEMPORARY'
                         AND ts.tablespace_name = ss.tablespace_name)
                   / 1024
                   / 1024 used_temp_mb
             FROM v$sort_segment ss
         GROUP BY ss.tablespace_name) u
 WHERE t.tablespace_name = u.tablespace_name

-- show temp space usage by session 
SELECT   su.TABLESPACE
        --,su.segtype
,        SUM (su.blocks * ts.block_size) / 1024 / 1024 mb
        ,se.SID
        ,se.serial#
        ,se.username
        ,se.status
        ,se.osuser
        ,se.machine
        ,se.program
        ,se.action
        ,sq.sql_text
    FROM v$sort_usage su
        ,v$session se
        ,dba_tablespaces ts
        ,v$sql sq
   WHERE su.session_addr = se.saddr
     AND ts.tablespace_name = su.TABLESPACE
     AND ts.CONTENTS = 'TEMPORARY'
     AND se.sql_address = sq.address(+)
     AND se.sql_hash_value = sq.hash_value(+)
GROUP BY su.TABLESPACE
        ,se.SID
        ,se.serial#
        ,se.username
        ,se.status
        ,se.osuser
        ,se.machine
        ,se.program
        ,se.action
        ,sq.sql_text
ORDER BY 2 DESC;

Ref:
1. Script - Temporary tablespace usage
http://gavinsoorma.com/2009/06/temp-tablespace-usage/