Q: What can be done prior to raise Windows function level?
A: Verify that Active Directory is replicating properly to all DCs. The Domain and Forest Functional Levels are essentially just attributes in Active Directory. The Domain Functional Level for all domains must be properly replicated before you’ll be able to raise the Forest Functional level. This practice also addresses the question of how long one should wait to raise the Forest Functional Level after you’ve raised the Domain Functional Level for all the domains in the forest. Well…what is your end-to-end replication latency? How long does it take a change to replicate to all the DCs in the forest?