The use of xhost authentication and related X11 protocols are obsolete. You can use xauth authentication and ssh with X forwarding instead. Simply type "ssh -X oracle@remote_host", or "ssh -X oracle@localhost" if you are using the local server's console. When using ssh -X you should not set a DISPLAY variable as ssh -X takes care of it.
when am i using both of them commands
[root@localhost ~]# ssh -X oracle@remote_host
ssh: remote_host: Name or service not known
[root@localhost ~]# ssh -X oracle@localhost
The authenticity of host 'localhost (127.0.0.1)' can't be established.
RSA key fingerprint is 4d:ad:af:04:e1:0c:0e:4b:fa:c1:21:ea:5a:7c:34:09.
Are you sure you want to continue connecting (yes/no)?