IMPORTANT: This article contains information about modifying the Active Directory schema. If problems occur, a system backup, or reinstallation of your system, may be the only way to recover data.
CAUTION: You should use extreme caution when you make any changes to the Active Directory schema because the changes occur forest-wide, and you cannot remove objects and attributes that are added to the schema.
The extension or the modification of the Active Directory schema requires write access to the schema. This is enabled by means of the "Schema Update Allowed" registry key. Schema updates may be enabled by means of the Schema Management Console, or directly in the registry. The schema updates can only be enabled on the domain controller that holds the schema master role.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
Schema updates may be enabled by means of the Schema Management Console or by editing the registry.
To Enable Schema Updates by Means of the Schema Management Console:
At a command prompt, type:
NOTE: RegSvr32 has been successfully registered when a DllRegisterServer in schmmgmt.dll succeeded dialog box is displayed.
Open a new management console by clicking Start, click Run, and then type:
On the Console menu, click Add/Remove Snap-in.
Click Add to open the Add Standalone Snap-in dialog box.
Click Active Directory Schema, and then click Add.
"Active Directory Schema" is displayed in the Add/Remove snap-in. Click Close, and then click OK to return to the console.
Click Active Directory Schema so that the Classes and Attributes sections are displayed on the right-hand side.
Right-click Active Directory Schema and click Operations Master.
Click to select the Schema may be modified on this Domain Controller check box. Click OK, and then exit the console.
The schema may now be updated on the domain controller that holds the schema operations master role.
To Enable Schema Updates by Means of the Registry:
It is not recommended to enable schema updates by directly editing the "Schema Update Allowed" registry key. Schema updates should be enabled through the console method, whenever possible. If for some reason the console method cannot be used, the following registry key may be edited directly: