After upgrading your schema, you might want to raise your forest and domain functional levels. As a best practice, follow these practices:
- Before changing your forest functional level, take at least one domain controller offline from each domain in your forest.
- Before changing the domain functional level of any domain, take at least one domain controller offline from the domain.
In both cases, you should make sure that the domain controllers you take offline do not hold any flexible single master operations (FSMO) roles in the forest or domains.
Keep the domain controllers offline for 48 to 72 hours after changing functional levels; if no issues are found, you can return the offline domain controllers to service. If issues are discovered, however, you can use your offline domain controllers as the source for rebuilding servers if a rollback to a previous functional level is required.
Mitch Tulloch is a eight-time recipient of the Microsoft Most Valuable Professional (MVP) award and widely recognized expert on Windows administration, deployment and virtualization. This tip was excerpted from his new book Installing and Configuring Windows Server 2012 Training Guide published by Microsoft Press which is available from Amazon. For more tips by Mitch you can follow him on Twitter or friend him on Facebook.