SkieWhat is the impact preview before I change a policy?
The impact preview shows what a policy or app list change will touch before you save it: which groups use it and how many devices will be affected. It lets you catch a mistake, such as editing a shared policy that sixty tablets rely on, before any device receives the change.
Shared rules are powerful and easy to get wrong. One edit to a widely used policy can reach every group that points at it. The impact preview puts that reach in front of you at the moment of decision, so the question 'who does this change?' is answered before you press save, not after the complaints start.
It is used for policy edits and for app list changes. If you add a social app to a list used by several classes, the preview tells you how far that goes. If the number is bigger than you meant, you can fork the policy or list instead and attach the copy only where you want it.
The preview works hand in hand with the where-used view, which lists the groups attached to a policy or list at any time, and with the effective policy view, which shows the final merged rules on a group or device. Together they let an admin check before, during and after a change.
A practical tip: make it a rule that any edit to a library policy goes through the preview, and that anything affecting more than one school gets a second pair of eyes. Changes reach devices on their next sync, and a device that is offline applies them as soon as the network returns.