Operation Master Disaster Recovery
Failure of the PDC emulator can affect users immediately, you should seize the PDC emulator role as soon as possible.When a PDC emulator is unavailable, Windows NT 4.0 backup domain controllers,are unable to synchronize directory changes, and pre-Windows 2000 clients are unable change passwords. When the original PDC emulator is restored and connected to the network again, it will detect the presence of the new PDC emulator and give up the PDC emulator role. If desired, the PDC emulator role can be moved back to the original server after it is restored.
The schema master has an essential role in a Windows Server domain,but that is not used very often. The schema master is the only domain controller in which the schema can be changed. If the server fails, you will not be able to make changes to the schema,until it is restored,or until the role has been seized.Failure of a schema master does not affect users. You should wait and restore the schema master rather than seizing it. If you do seize the schema master role to another domain controller, the original schema master should never be restored on the network.
Domain Naming Master
The operations master is required only when adding or removing domains. The failure of this role does not affect users. Administrators are only affected if a new domain is being added to the forest or an old domain is being removed from the forest.You should wait for the original domain naming master to be restored.If you must add or remove a domain and you do not have time to restore the domain naming master, you can seize the role. If you do seize the domain naming master role to another domain controller, the original domain naming master should never be restored on the network
The infrastructure master role is maybe least important in a disaster recovery perspective. The infrastructure master monitors display-name changes for user and group accounts across multiple domains. This becomes an issue only when administrators are viewing group memberships.You should wait and restore the infrastructure master role rather than seizing. If you seize an infrastructure role to another domain controller in a multiple-domain environment, you should ensure that the destination domain controller is not a GC server. An infrastructure master placed on a global catalog server does not function properly. If you seize the role,you can restore the original infrastructure master.
The RID master assigns RID pools to other domain controllers as new security principals are created. If the RID master is not available for a long period, the domain controllers might run out of RIDs to assign to new security principals. This role only needs to be seized if you are planning to create a large number of security principals before the original RID masteris restored, or if you are not planning to restore the original RID master. If you seize the RID master role to another domain controller, the original RID master should never be restored on the network.