Well...

It is a hack !

As Martijn said, there is no way to prevent SYSDBA to connect, unless
you use this hack, and I should add "use it at your own risk".


To undo, as always, you will can extract a metadata back-up.
Create a new database
pump the data from the old database.

Anyway, I should tell you to try it on a database that you don't care
about, and see if if works, and if you can undo it if/when necessary.

see you !

--
Alexandre Benson Smith
Development
THOR Software e Comercial Ltda
Santo Andre - Sao Paulo - Brazil
www.thorsoftware.com.br