Oracle Undo tablespace users Can anybody help me on "what all users are using the undo tablespace and how much" in oracle database 11g r2. any pointers would be much appreciated.
This shows you the amount of undo size used by each session that is currently active.

select s.sid, 
       s.username,
       sum(ss.value) / 1024 / 1024 as undo_size_mb
from  v$sesstat ss
  join v$session s on s.sid = ss.sid
  join v$statname stat on stat.statistic# = ss.statistic#
where stat.name = 'undo change vector size'
and s.type &lt;&gt; 'BACKGROUND'
and s.username IS NOT NULL
group by s.sid, s.username;