Oracle Temporary table Space reasons for excessive use and sizing
you can use this query to find whats exactly is filling temp tablespace

SELECT a.username, a.SID, a.serial#, a.osuser, b.TABLESPACE, b.blocks,
c.sql_text
FROM v$session a, v$tempseg_usage b, v$sqlarea c
WHERE a.saddr = b.session_addr
AND c.address = a.sql_address
AND c.hash_value = a.sql_hash_value
ORDER BY b.TABLESPACE, b.blocks;