Ever wanted to know who was logged into your oracle server and where
from? This SQL will show you the username connected, which machine they
are connected from and what time they connected.
SELECT s.username, s.program, s.logon_time FROM v$session s, v$process p, sys.v_$sess_io si WHERE s.paddr = p.addr(+) AND si.sid(+) = s.sid AND s.type='USER';