Below script can be used to find the active transactions in the oracle database.

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,, t.used_ublk "USED BLKS", 
decode(, '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