Where are plan views stored?

I created a child project area that was inheriting from a parent project area.  Inheritance was broken between the child project and parent such that the child was able to customize its plan views and plan types. Several new plan views were created.  I restored inheritance to the child project area by editing the plan information from  its XML.  I expected to see that plan views were no longer available to the child project area, but instead they were still there.  This makes me wonder why they are still there and where they are stored.