In the Windows Server 2003 family, you can restore the Active Directory database if it becomes corrupted or is destroyed because of hardware or software failures. You must restore the Active Directory database when objects in Active Directory are changed or deleted.
Note: There is an option to restore Active Directory objects that have been deleted and are now in a phase called “tombstone”. These items are hidden from the GUI and await their cleanup by a process called “garbage collection”. Read more about it on my “Recovering Deleted Items in Active Directory” article.
You can use one of the three methods to restore Active Directory from backup media: Primary Restore, Normal Restore (i.e. Non Authoritative), and Authoritative Restore.
For example, if you inadvertently delete or modify objects in Active Directory, and those objects were thereafter replicated to other DCs, you will need to authoritatively restore those objects so they are replicated or distributed to the other servers. If you do not authoritatively restore the objects, they will never get replicated or distributed to your other servers because they will appear to be older than the objects currently on your other DCs. Using the NTDSUTIL utility to mark objects for authoritative restore ensures that the data you want to restore gets replicated or distributed throughout your organization.
On the other hand, if your system disk has failed or the Active Directory database is corrupted, then you can simply restore the data normally without using NTDSUTIL. After rebooting the DC, it will receive newer updates from other DCs.