To find out the users connected to Oracle Applications Release 11i:

select distinct raf.user_name User_Name,raf.RESPONSIBILITY_KEY Responsibility
from fnd_user raf,
fnd_responsibility raf, icx_sessions hussain
where raf.user_id = hussain.user_id AND
raf.responsibility_id = hussain.responsibility_id AND
hussain.disabled_flag='N' AND
hussain.responsibility_id is not null AND
hussain.last_connect like sysdate;