3.1.1.5.5.3 Protected Objects
The following objects are considered protected and cannot be deleted:
The DC's rIDSet object and all of its ancestors. A DC's rIDSet object is the referent of the rIDSetReferences attribute of the DC's Domain Controller object (section 6.1.1.3.1).
The crossRef objects corresponding to the DC's config, schema, and default domain NCs.