Dynamics 2011 - Cannot Delete Relationship!

Recently we ran into a really interesting problem within our company when trying to delete a relationship between 2 entities. We kept getting 1 of 2 errors:

1. Cannot delete EntityRelationship because one or more components require it.
 
2. An error about an attributemap that no longer existed (I couldn't recreate this error to get the exact wording)

Obviously you'll have checked for the obvious like ensuring the field doesn't exist on a form or removing any connections if applicable. None of this solves the problem, so what could it be?

One of the most common reasons I've found is you've edited the site map and changed where the related link is displayed. So let's say you have an entity called Product and one called Component referencing it (i.e. Component has a look up to Product). There will also be a related list/link on the left navigation of Product where you can see all of it's Components. If you use a sitemap editor to reorder or change how this is displayed this can cause you a problem when trying to delete the relationship.

The second problem is quite an unusual, and I'm not sure why dynamics doesn't automatically do this for you. Let's go back to our example above but add a third entity:

1. Supplier
2. Product (Which has a look up to the Supplier entity)
3. Component (Which has a look up to the Product and Supplier entity)


Here's the scenario I came across, I try to delete the relationship between Product and Supplier and it says:

But what else could possibly require this? I click on details within the error and it points me to the relationship between Product and Component... ok, so what's going on here then?

9 times out of 10 you've added a mapping. In my case whenever I created a new Component from the Product screen I had a mapping to automatically use the supplier from Product to populate Component. So, open up that relationship and check for any mappings! Dynamics should really remove this mapping for you, but such is life.

Just a few things to be aware of when working with relationships.