All schema extensions (adding classes, subclasses, or attributes) are irreversible and permanent. After they're added, objects can never be removed from the schema. However, they can be deactivated, if they were not part of the default schema and are not currently in use in the schema. If you want to deactivate an attribute you have added, you must make sure you have first deactivated any classes that use that attribute. If you do not, you will receive the error message shown in Figure 13.15. To deactivate an attribute, follow these steps:
Open the AD Schema MMC Snap-in.
Double-click the attribute.
Select the Deactivate This Attribute check box and click OK.
Figure 13.15. The error message.
After you ...