In a multiple-master replication environment, any domain controller can theoretically change any object in Active Directory. As we saw in the last chapter, Active Directory has special features to handle conflicting updates performed during the same replication interval.
Certain Active Directory functions just cannot be shared without causing potential data consistency problems. These special functions are called Flexible Single Master Operations, or FSMOs (pronounced FizzMohs). The domain controller assigned a particular FSMO is called a role master. Here are the five FSMOs and the MMC console you would use to view and set the role master:
PDC Emulator— AD Users and Computers
RID Master— AD Users and Computers ...