When you need to apply an ExamSys update that involves the database going offline you will need to ensure that your site notifies your users what is going on.
We have provided in the root .htacess file an example of how you can redirect all traffic to a maintenance page. Your site administrator may have a different preferred method.
If the ExamSys update does not require the database to to go offline. You can place ExamSys in maintenance mode in the configuration screen. This will restrict access to the site to system administrators only.