We are completely redeveloping a website that has a DMX repository (Version 5.03). This work is being done on DNN 5.06 as another portal on the same installation. A Large number of categories exists and users. We are expanding the use of the repository with new products, documents, and categories.

I am upgrading to DNN 6.02 and DMX 6.0.0.2. (latest versions)

All Backups done.
When the time comes How do I move the documents/categories in DMX to the new portal?

This is a FAQ. The bottom line is that there is no way to migrate the metadata of DMX from one portal to another. The reason is that DMX's data is linked to users, roles and other objects in DNN that are unique to each portal. Even if you'd have an exact copy the IDs of these objects are different. So moving content is impossible.

The only way to migrate the DMX contents is by exporting and importing with the built in DMX scripts. So you export the contents of DMX using a script under Admin > Run Scripts. The complete DMX will be pumped out to portals/[id]/DMX/Export. Then you copy that over to your destination server and use DMX's import function to import it again. Note you'll lose the metadata like categories, permissions, etc.

For anyone else reading this: the preferred way is to always keep using your old installation and upgrade your way to what you need. But I understand that there are projects where this is impossible.

Peter