Importing metadata from Oracle database seems to take longer than any other database, when the underlying the schema is large. This may be because the default settings with Oracle Driver tries to get lot more metadata then needed. Should explore ways to minimize the time to take import.

Teiid in the Dynamic VDB import uses "Table Types" and "schema" name to limit the number of tables it imports, may be we should adopt similar thing in Designer. It is possible that Designer is already doing such settings.