Attempting to delete a domain on the Administration Console;
However the following error appears:
This usually means the domain is still tied to something else, for example, a realm, a policy, a role, etc
The first thing to do is check the obvious places on the Admin Console
Authentication > Realms
Check under the domains column...
If you see it in there (as per the example above), edit the realm and remove it.
Administration>Policies
Check all domain/group/user policies that you may have created or edited recently
Administration>Roles
Check if any roles are tied to a domain