raise forest functional level

Tien Ngo Thanh 

Hi,

usually, not much to do, but you need to confirm that the application in your environment and infrastructure are compatible with don't have any issue with this, one of the application is Exchange, Check this https://docs.microsoft.com/en-us/exchange/plan-and-deploy/supportability-matrix?view=exchserver-2019

Also, you need to make sure that you DONT have any domain controller older than the function level you will have, check this here https://docs.microsoft.com/en-us/troubleshoot/windows-server/identity/raise-active-directory-domain-forest-functional-levels

To downgrade, I don't think there is a possible way to downgrade easily, its one way, but if you still need to downgrade, you will need to do Forest Recovery, But this site talks about how to downgrade

https://azurecloudai.blog/2019/10/23/downgrading-active-directory-domain-and-forest-functional-levels-part-1/

I did not try these steps so you do the restoration at your own risk.

most of other application usually do basic Read/Write operation to AD and wont care much about the AD Forst Function level,