Failing over to a replicated a Domain Controller (4042603)

You need to failover to a replicated Domain Controller.

Just failing over to a replicated Domain Controller can cause that Domain Controller to be out sync.
 

You have replicated a domain Domain Controller and now need to perform a failover be aware that additional steps after the vRanger failover will need to be performed to get the Domain Controller to work correctly. The Ntdsutil tool will need to be used to complete the reconfiguration of the Domain Controller. Please take a look at the following Microsoft link about how to use the Ntdsutil tool.
http://technet.microsoft.com/en-us/library/cc976711.aspx