By default, the Active Directory Schema MMC snap-in is not registered on domain controllers or machines with the Remote Server Administration Tools (RSAT) installed. To use the snap-in for the first time on a new machine, you’ll need to register the DLL. To do this, follow the steps below:

  1. Open an elevated command prompt
  2. Run the following command: regsvr32 schmmgmt.dll
  3. You should receive a success message:

DllRegisterServer in schmmgmt.dll succeeded.

Once you have registered the snap-in, you can add it to an MMC by following these steps:

  1. Open a new MMC Console (Start>Run>mmc)
  2. In the MMC Console, go to File>Add/Remove Snap-in
  3. Add the Active Directory Schema snap-in as shown below:

Active Directory Schema Snap-In

Once you click OK, you’ll be able to access the snap-in through the MMC Console.