The key to a successful migration from Windows NT 4.0 domains to Windows 2000 Active Directory domains is planning. There are several important stages or elements of migration planning that should not be avoided.
First, you must determine whether or not the existing domain structure is sufficient for your organization. If not, you'll not only need to upgrade, you will also need to restructure. In most cases, restructuring is best accomplished after the upgrade migration is complete.
Second, you need to plan the order of the upgrade. In a multi-domain environment, you should always upgrade the account domains before any resource domains. Within each domain, upgrade the PDC first, followed by the BDCs.
Third, decide when to switch to native mode from mixed mode. Native mode offers full access to Windows 2000's Active Directory capabilities. However, you cannot upgrade a domain to native mode until all domain controllers are Windows 2000.
Fourth, you need to decide when to upgrade member servers and clients. The upgrading of non-domain controller systems is inconsequential to the domain structure. So, upgrading clients and member servers can be placed at the end of the upgrade process.
Fortunately, the migration from Windows NT domains to Windows 2000 AD domains does not need to occur all at once. In fact, performing the migration in stages circumvents more problems than performing the migration all at once. Once the PDC in a domain is upgraded from Windows NT to Windows 2000, it continues to support the Windows NT BDCs. Once you are sure your new Windows 2000 AD domain controller is stable, you can elect to upgrade the BDCs one at a time. Once all BDCs are upgraded, you can then elect to switch to native mode.
James Michael Stewart is a researcher and writer for Lanwrights, Inc.