I've done a few domain migrations (merge child into parent) successfully using ADMT, however all have involved only a single DC on the child side. My next migration has 2 DC's in the child. My question is how should I do the migration? Should I demote both DC's at the same time? Should I demote one then promote it to the new domain before doing the other? If I do them one at a time I'd assume the server holding the operations masters roles should be done second?