You now have less downtime when you change a MySQL Configuration. MySQL Database Service automatically distinguishes the variables that can be changed dynamically from those that require a restart. If the current and the selected configurations differ in dynamic variables only, the configuration is updated without restarting the database. Changes to variables that are not dynamic restart the database and the Console displays a warning. For more information, see Advanced Option: Configuration. 

You can change configurations in the Console by using the Edit DB System panel. For more information, see Editing a DB System.