If you try to delete an entity related to other entities such as, for example (but many other situations may occur):
The Model Structure will mark the constraint that is causing this behavior with a red arrow.
The Delete dialog box will be displayed offering the following options:
Delete related entity too | If you use the OK button and the entity you selected has more than one relation, the dialog box will de displayed as many times as the number of relations. To delete all related entities with just one click, select All. If the Delete related entity too option is not selected, the All button is grayed out. |
Unlink reference | If you use the OK button, related entities will be unlinked one at a time. To unlink all related entities with just one click, select All. In this case, if for any reason one related entity cannot be unlinked, the dialog box will be displayed again. |