Active Directory Migration Tool overview

Use Active Directory Migration Tool to migrate user accounts, groups, and computer accounts:

• From Windows NT 4.0 domains to an Active Directory domain environment (interforest).
• Between Active Directory domains in different forests (interforest).
• Between Active Directory domains in the same forest (intraforest).

Domain migration is achieved by upgrading a Windows NT domain structure to to an Active Directory environment or as part of an Active Directory domain restructure. Active Directory Migration Tool is used to migrate existing Windows NT 4.0 domains into Active Directory environments. It can also be used to consolidate one or more Active Directory domains into a single domain.

By using a domain restructure, you can redesign your existing domain structure to better meet the needs of your organization. Though restructure can result in any number of different outcomes, typically the result is a change in the logical relationship between your domains, and often fewer domains.

The recommended way to redesign your domain structure is to design and build a new Active Directory forest separate from your existing domain structure and then, using Active Directory Migration Tool, migrate user accounts, groups, and computer accounts in stages from your production environment to the new Active Directory forest. Eventually, you decommission the old domain structure.

Domain upgrade, or in-place upgrade, involves upgrading each domain's primary domain controller and eventually upgrading all of the backup domain controllers. Using this method, you can upgrade all of your domains directly into a new Active Directory forest. A domain upgrade retains your current domain structure and no migration takes place. Active Directory Migration Tool does not support this process. However, after upgrading all Windows NT domains, you can redesign your upgraded domain structure by creating a new forest and using Active Directory Migration Tool to migrate the upgraded domains into the new forest. For more information about domain upgrade, see Windows Server 2003 Help.

When migrating objects from computers in a source domain to a target domain, Active Directory Migration Tool installs services, called agents, on the source computers. These agents are dispatched from the computer on which Active Directory Migration Tool is running and are installed on other computers using the security credentials of the user account used to run Active Directory Migration Tool. Once installed, the agents run as a service using the local system security credentials. There is no need to load software on the source computers prior to the migration.

For more information on Active Directory Migration Tool, see Understanding Active Directory Migration Tool.