How to find the active transaction in Oracle database

Script can be used to find the active transactions.

col name format a10 
col username format a8 
col osuser format a8 
col start_time format a17 
col status format a12 
tti 'Active transactions' 

select s.sid,username,t.start_time, r.name, t.used_ublk "USED BLKS", 
decode(t.space, 'YES', 'SPACE TX', 
decode(t.recursive, 'YES', 'RECURSIVE TX', 
decode(t.noundo, 'YES', 'NO UNDO TX', t.status) 
)) status 
from sys.v_$transaction t, sys.v_$rollname r, sys.v_$session s 
where t.xidusn = r.usn 
and t.ses_addr = s.saddr;