To save space in the databases, and improve search performance, you should not use more metadata than you really need. The maximum limit is 750 metadata per document type.
You must create a global resource set for all document types and metadata groups used within an organization. This ensures that all document types, metadata groups, and metadata are unique.
To create a global resource set, you can create a separate Design Center Project, and create the global resource set in this Project. You then add the global resource set to all your Design Center Projects. In each Project, you connect the document type resources to the appropriate Message configurations and Runtime configurations. For example, connect an Invoice document type resource to a Message configuration that produces invoices, and an Order document type resource to a Message configuration that produces orders.