|System Settings, Defaults, Clusters, and Active Directory Authentication / Setting System Defaults|
You can use the Defaults screen in the Administration Console to change a default setting at any time.
Changes update the server as soon as you save them, but they do not affect existing users unless you set Override User Settings to Yes. By default, Override User Settings is set to No for all default settings.
The overrides let you establish baseline system settings at any time. For example, to turn off the alert tones that announce a text message, you would deselect the Text Message Alert property on the Notifications page and set Override User Settings for that property to Yes. This change would affect all new and existing users.
If you later want to allow users to customize this property, set Override User Settings for the Text Message Alert property to No. The alert tones for all users remain turned off until they manually enable them again.