We created relations on the EDT level in the AX 2009. In Microsoft Dynamics AX 2012, relations can no longer be created under extended data type (EDT) nodes in the Application Object Tree (AOT). Relations that are defined under EDT nodes are still effective, but in a future release they will be obsolete and deleted. The EDT relation migration tool helps you move relations from EDT nodes to table nodes. The EDT relation migration tool is found on the client menu, under
Tools > Code upgrade > EDT relation migration tool.
see more details in the below link.
http://msdn.microsoft.com/en-us/library/gg989788.aspx
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