It is also highly encouraged to restrict access to your website while repairing the database or making upgrade. Here is an example of restricting your website instance to your IP address exclusively. Other visitors, including search spiders, will get the HTTP 503 Service Unavailable error.
Create a file 503.php in your website root:
your IP-address.
Once you save this .htaccess file or reload Apache configuration, your site will be down until you restore the initial state.