Команды для анализа использования UNDOTBS

Display sizes of active, unexpired and expired UNDO extents

select status, round(sum(bytes)/1024/1024) as "Size, MB" from dba_undo_extents group by status;

Display UNDO utilization details per user session (SID, User Name)

select a.sid, a.username, a.osuser, round(b.used_ublk*8/1024) as "RBS Size, MB",
  b.used_urec as "Undo records", "RBS Name", b.start_time
from v$session a, v$transaction b, v$rollname c
where b.addr = a.taddr and c.usn = b.xidusn;