Show temp tablespace usage

SELECT b.tablespace,
       ROUND(((b.blocks*p.value)/1024/1024),2)||'M' AS temp_size,
       a.inst_id as Instance,
       a.sid||','||a.serial# AS sid_serial,
       NVL(a.username, '(oracle)') AS username,
       a.program,
       a.status,
       a.sql_id
  FROM gv$session a,
       gv$sort_usage b,
       gv$parameter p
 WHERE p.name  = 'db_block_size'
   AND a.saddr = b.session_addr
   AND a.inst_id=b.inst_id
   AND a.inst_id=p.inst_id
 ORDER BY b.tablespace, b.blocks;