New Features in Windows Server 2003
The only new feature in Windows Server 2003 that affects Active Directory failure and recovery is the new capability of domain controllers that are not Global Catalog servers to cache Universal group membership. The GC holds the membership lists for Universal groups, and without this information, a domain controller refuses to let users authenticate. Ordinarily, a loss of connection to GC servers, such as might happen with a T1 cut, would result in users being unable to log on to the domain. By caching Universal group membership on standard domain controllers, the loss of access to GCs does not result in a loss of domain access.