SELECT s.sid, s.serial#, t.start_time, t.xidusn
  FROM v$session s, v$transaction t, v$rollstat r
  WHERE s.saddr = t.ses_addr
  AND t.xidusn = r.usn
  AND ((r.curext = t.start_uext-1) OR
  ((r.curext = r.extents-1) AND t.start_uext=0));
