Oracle : Script to Monitor User Activity in database

set pagesize 66
col c1 for a9
col c1 heading "OS User"
col c2 for a9
col c2 heading "Oracle User"
col b1 for a9
col b1 heading "Unix PID"
col b2 for 9999 justify left
col b2 heading "SID"
col b3 for 99999 justify left
col b3 heading "SERIAL#"
col sql_text for a35
break on b1 nodup on c1 nodup on c2 nodup on b2 nodup on b3 skip 3
select c.spid b1, b.osuser c1, b.username c2, b.sid b2, b.serial# b3,
a.sql_text
  from v$sqltext a, v$session b, v$process c
   where a.address    = b.sql_address
--   and b.status     = 'ACTIVE' /* YOU CAN CHOOSE THIS OPTION ONLY TO SEE
--                                  ACTVE TRANSACTION ON THAT MOMENT */
   and b.paddr      = c.addr
   and a.hash_value = b.sql_hash_value
 order by c.spid,a.hash_value,a.piece
/