Generally, we can login the oracle by os authentication, if we login os in a remote machine and make it os to an authentication.
In ordert to come true this function, it should configure parameter OS_AUTHENY_PREFIX configure a prefix such as OS_AUTHENT_PREFIX=RAY$, when we login oracle using a remote machine who's os name is SUN, the oracle make the os name is RAY$SUN. Then it will compare the os authentication record.
You also need configure the parameter REMOTE_OS_AUTHENT = true
example:
CREATE USER RAY$SUN IDENTIFIED BY EXTERNAL;