If you running UNIX use these 2 scripts together to find out what is using temp space. This works on 8.0, don't know about 8.1 (assuming you have an OPS$ORACLE user)
Alex
sqlplus / << EOF
set line 130
set pagesize 100
set feedback off
column tablespace format a10
select user, session_num, sqlhash, extents, blocks, tablespace from v\$sort_usage
/
EOF
echo "Enter hash value"
read HASH
sqlplus / << EOF
set line 130
set pagesize 100
set feedback off
column tablespace format a10
select osuser, process from v\$session where sql_hash_value like '%$HASH%'
/
EOF