When the domain controller that holds a FSMO role is no longer available and there is no prospect that the domain controller will ever be restored, then transferring the FSMO role is no longer an option. In this case, seizing the FSMO role is the best way to go.
Seizing FSMO roles
Getting ready
To seize the Schema Master and/or Domain Naming Master FSMO roles, you'll need to be signed in with an account that is a member of the Enterprise Admins group. To seize the other FSMO roles, you'll need to be signed in with an account that is a member of the Domain Admins group.
