Raise Forest Functional Level Dialog Box

Note

After you set the forest functional level to a certain value, you cannot roll back or lower the forest functional level, with one exception: when you raise the forest functional level to Windows Server 2008 R2 and if Active Directory Recycle Bin is not enabled, you have the option of rolling the forest functional level back to Windows Server 2008. (For more information about Active Directory Recycle Bin, see What's New in AD DS: Active Directory Recycle Bin (https://go.microsoft.com/fwlink/?LinkId=141392)).
You can lower the forest functional level only from Windows Server 2008 R2 to Windows Server 2008. If the forest functional level is set to Windows Server 2008 R2, it cannot be rolled back, for example, to Windows Server 2003.