Error when trying to delete Monitored By attribute from CIT Node

Hi,

I'm trying to delete Monitored By attribute on CIT Node in my UCMDB class model.

But when I try to do that I'm getting this type of error message:

This method is not supported for aggregated-derived-concrete-layout

Part of UCMDB server error log is attached. 

Why I'm deleting Monitored By attribute is that I'm trying to create it on parent InfrastructureElement CIT because of NNM push integration which prerequisite is that Monitored By attribute exists.