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Adjust Forest Functional Level

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Applies To: Windows Server 2008, Windows Server 2008 R2

You can use this procedure to adjust the forest functional level for a domain rename operation. The domain rename operation is supported within an Active Directory forest if, and only if, all domain controllers in the forest are running Windows Server 2003 or Windows Server 2008 Standard Edition, Windows Server 2003 or Windows Server 2008 Enterprise Edition, or Windows Server 2003 or Windows Server 2008 Datacenter Edition, and the forest functionality has been raised to Windows Server 2003 or Windows Server 2008. Therefore, before you can rename a domain in your Active Directory forest, you must ensure that the forest functionality has been set to at least Windows Server 2003 or raised to Windows Server 2008.

Setting forest functional level to Windows Server 2003 or Windows Server 2008

You can set the forest functional level to Windows Server 2003 if all domain controllers in the forest run either Windows Server 2003 or Windows Server 2008 operating systems. If any domain controller in the forest is still running Windows 2000, you cannot set the forest functional level to Windows Server 2003.

You can set the forest functional level to Windows Server 2008 if all domain controllers in the forest run Windows Server 2008 operating system. If any domain controller in the forest is still running Windows Server 2003, you cannot set the forest functional level to Windows Server 2008.

For more information, see Understanding AD DS Functional Levels (https://go.microsoft.com/fwlink/?LinkId=124107).

To set the forest functional level to Windows Server 2003 or Windows Server 2008

  1. Open the Active Directory Domains and Trusts snap-in: click Start, click Administrative Tools, and then click Active Directory Domains and Trusts.

  2. In the console tree, right-click Active Directory Domains and Trusts, and then click Raise Forest Functional Level.

  3. In Select an available forest functional level, do one of the following:

    • To raise the forest functional level to Windows Server 2003, click Windows Server 2003, and then click Raise.

    • To raise the forest functional level to Windows Server 2008, click Windows Server 2008, and then click Raise.

Warning

Do not raise the forest functional level to Windows Server 2008 if you have, or will have, any domain controllers that are running Windows Server 2003 or earlier. After you raise the forest functional level to Windows Server 2008, you cannot change the level back to Windows Server 2003.