Domain migration (merge child into parent) question

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?
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It is the same process. install ADMT and point it at one of the DC's and migrate the accounts to the new domain, the two DC's should both be synchronized and will contain the same data.

To move one of the DC's you need to move all the FSMO roles to the other DC:

Then demote the server and then you can add this to the new domain.

Of course if the DC's are the last computers, servers and users in the domain and all data has been moved you could remove the trusts to any other domains and just re-format the servers for whatever use you want as there will be nothing that relies on the servers.
Tofu4679Author Commented:
The 2 DC's in the child domain are being promoted to DC's in the new domain after they've been demoted.  Just wondering if there is an order that should be followed or if it doesn't really matter.
I believe that you would have potential problems trying to demote the last two DC's in a domain at the same time and would have to use the /forceremoval option to complete the task.

This is why you would normally move the FSMO roles off the first DC to be demoted, and then wait for the changes to replicate before running dcpromo to demote the server.

When you run this on the last DC in the domain it would ask you if this was the last DC server in the domain and should not therefore cause any errors.

This is the recommended way to collapse the domain.

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Tofu4679Author Commented:
Thanks, all the FSMO roles are already on one of the servers so I'll just do that one last and close out the domain when I demote it.
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