select S.Username,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)) )