The documentation portal is undergoing maintenance. During this period, you can't create any new user credentials. If you do, you'll need to recreate the user credential after the maintenance period ends.
The SAP R/3 model includes a class named SAP Schema. Metadata Manager uses this class to display data lineage between SAP R/3 and PowerCenter repository objects. It is not displayed in the metadata catalog when you load an SAP R/3 resource.