Installing Oracle DataBase 11.2.0.3.2 on Oracle Linux 6.3 - Disable Remote Root Login to the Database Server

# vi /etc/ssh/sshd_config

Change

#PermitRootLogin yes

to

PermitRootLogin no

# service sshd restart

I recommend going directly to the latest version of the document, which uses newer software versions

Link to the Oracle installation document.