Temp space filled up

   I am getting the ora-01652 unable to extend temp segment by 12800 in tablesapce Temp error in the alert log.

My environment is oracle RDBMS version 10.2.0.3 on solaris 10.

Is there a way to find out which user is filling up the temp?

I have issued the following query:

select sum(free_blocks) from gv$sor_segment where tablespace_name ='TEMP'

 and

select inst_id, tablespace_name, total_blocks, used_blocks, free_blocks from gv$sort_segment;

The results showed that there are still free blocks there. If I can find out which session or which user is filling up the temp, then I might be able to find out what he/she is running and I might be able to adjust the temp file size accordingly. Thanks.