Configuration driven Active Directory management.
The Forest Level Component enables defining a desired functional level for the managed forest. The functional level defines what Active Directory features are available to the forest.
To do define the Forest Level, place a file named firest_level.json straight in the forest folder.
This file should be a simple json object with a single property: Level.
Example content:
{
"Level": "2016"
}
Supported values: 2008R2, 2012, 2012R2 or 2016
It is impossible to downgrade a forest functional level, so even if you define a low level, it will not be applied if the domain is already at a higher level.
It is impossible to upgrade the forest to a level not yet reached by all member domains. In order to upgrade the forest functional level, be sure to first update every single domain.