Show session information for a pending transaction

select s.sid,
       s.serial#,
       s.username,
       s.machine,
       s.status,
       s.lockwait,
       t.used_ublk,
       t.used_urec,
       t.start_time
       from v$transaction t 
       inner join v$session s on t.addr = s.taddr;

Example:

       SID    SERIAL# USERNAME   MACHINE   STATUS   LOCKWAIT          USED_UBLK  USED_UREC START_TIME
---------- ---------- --------   --------- -------- ---------------- ---------- ---------- --------------------
        29       7789 SYS        thehost   ACTIVE                             1          2 04/07/11 21:26:29