Where in migration process does old server stop functioning as primary server?

Question

I am migrating from a SBS 2003 box to a new WS 2012 R2 Essentials box - following the instructions from 
"Migrate from Previous Versions to Windows Server 2012 R2 Essentials or Windows Server Essentials Experience".   What I need to know is where in the process does
the old server stop functioning as a server for my network.   What I mean by this is when in the migration process (when I add the new server as a replicate DC?  not until I demote the old server?) will any programs/databases on the old server no
longer be available to client computers?  
Thanks for any insight.

Answer 1

Yeah, we need to agree on what is meant by "the server". In Windows, Server means many different things. Each time you move, a role or feature from the "old" to the "new" the old server ceases to function as "the server"
for that role or feature. The basic functions of a Windows DC include Active Directory, 5 FSMO roles, file and print services, and application services to name just a few.
So the answer to your question is more to do with what you mean by "server".  In particular, for the application role, you must move the app to the new server by whatever means the developer recommends.  At that point, regardless of whatever
else is going on the old server is out of the picture for that application.
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