View what sql user is running

-- View SQL text for user session
-- Replace DB_USER with the actuall database username and os_user with the OS username.

select a.sql_text, b.username, b.osuser, b.logon_time, b.program,
        b.machine, b.sid, b.serial# 
from v$sql a, v$session b
where a.address = b.sql_address
and b.username = 'DB_USER'
and b.osuser = 'os_user';