Flaxible Single Operations master
A domain controller that has been assigned one or more special roles in an Active Directory domain. The domain controllers assigned these roles perform operations that are single-master (not permitted to occur at different places on the network at the same time). Examples of these operations include resource identifier allocation, schema modification, PDC emulation, adding and removing domains to and from the forest, and tracking changes to security principals across all domains in a forest.
1.Schema master
A domain controller that holds the schema operations master role in Active Directory. The schema master performs write operations to the directory schema and replicates updates to all other domain controllers in the forest. At any time, the schema master role can be assigned to only one domain controller in the forest.
2.Domain naming master
A domain controller that holds the domain naming operations master role in Active Directory. The domain naming master controls the addition or removal of domains in the forest. At any time, the domain naming master role can be assigned to only one domain controller in the forest.
3.RID master
A domain controller that holds the RID operations master role in Active Directory. The RID master is assigned to allocate unique sequences of relative IDs to each domain controller in its domain. As the domain controllers use the IDs allocated, they contact the RID master and are allocated additional sequences as needed. At any time, the RID master role can be assigned to only one domain controller in each domain.
4.PDC emulator master
A domain controller that holds the PDC emulator operations master role in Active Directory. The PDC emulator services network clients that do not have Active Directory client software installed, and it replicates directory changes to any Windows NT backup domain controllers (BDCs) in the domain.
The PDC emulator handles password authentication requests involving passwords that have recently changed and not yet been replicated throughout the domain. At any time, the PDC emulator master role can be assigned to only one domain controller in each domain.
5.Infrastructure master
A domain controller that holds the infrastructure operations master role in Active Directory. The infrastructure master updates the group-to-user reference whenever group memberships change and replicates these changes across the domain. At any time, the infrastructure master role can be assigned to only one domain controller in each domain.
