Password File

Create Password File.
orapwd file=password_file_name password=the_secret_password
orapwd file=password_file_name password=the_secret_password entries=n

Add users to password files:
grant sysdba to "user"
grant sysoper to "user"

View users who have SYSDBA or SYSOPER priv:
select * from v$pwfile_users;

Connect:
sqlplus ""user" as sysdba"

note:
in 9.2, connection info shows connection as sys.
in 8.1.x, connection info shows connection as self.