Hi,

Below is few methods to cleanup metadata. 

#Using GUI:

1. To remove the failed server object from the domain controller’s container
2. Go to Start à Admin tools à Active Directory Users and Computers
3. In Active Directory Users and Computers, expand the ‘Domain Controllers’ OU.
4. Delete the computer object associated with the failed domain controller.
5. If you get a prompt saying you want to delete the server object without performing a DCPROMO operation be sure to check “This DC is permanently offline…” before clicking on the delete button
6. Windows will prompt you again like you don’t know what you are doing, so go ahead and click yes on the next prompt if you get it.

Note: Metadata cleanup is automated with windows server 2008. We just need to delete the computer object from the Domain Controllers OU using ADUC from a Windows Server 2008 machine and the metadata cleanup process occurs automatically.

Ref: https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/cc816907(v=ws.10)

#Using ntdsutil:

1. At the command line, type Ntdsutil and press ENTER.
2. At the Ntdsutil: prompt, type metadata cleanup and press Enter.
3. At the metadata cleanup: prompt, type connections and press Enter.
4. Type connect to server <servername>, where <servername> is the domain controller that is still alive. Press Enter.
5. Type ‘q’ and press Enter to return you to the metadata cleanup: prompt.
6. Type select operation target and press Enter.
7. Type list domains and press Enter.
8. Type select domain <number>, where <number> is the number corresponding to the domain in which the failed server was located. Press Enter.
9. Type list sites and press Enter.
10. Type select site <number>, where <number> refers to the number of the site in which the domain controller was a member. Press Enter. We will use site 0.
11. Type list servers in site and press Enter. This will list all servers in that site with a corresponding integer.
12. Type select server<number> and press Enter, where <number> refers to the domain controller to be removed.
13. Type ‘q’ and press Enter. The Metadata cleanup menu is displayed.
14. Type remove selected server and press Enter.
15. You will receive a warning message. Click Yes.
16. At this point, Active Directory confirms that the domain controller was removed successfully.
17. Type “q” and hit enter until you return to the command prompt.
18.  

#Cleanup from Sites and Services:

To remove the failed server object from the sites and services

1. Go to Start à Admin tools à Active Directory Sites and Services
2. In Active Directory Sites and Services, expand appropriate site,
3. Delete the server object associated with the failed domain controller.

#Cleanup from DNS:

1. Go to Start à Admin tools à DNS
2. Remove the CNAME for failed DC in the _msdcs. You should also delete the HOSTNAME and other DNS records.
3. Remove this server from being a name server on any of the zones
4. Remove the PTR record associated with this zone

Ref: https://support.microsoft.com/en-us/help/216498/how-to-remove-data-in-active-directory-after-an-unsuccessful-domain-co

Hope it helps you.

Excellent !!