>After I have the data from the Oracle DB in a CA cursor, is the sys(3054) function usable for subsequent queries?

Yes. As stated before it only works with Native DBF (tables or cursors). If you query data from Oracle and now you have it locally (dbf) it will then report on it. Of course you'd have to index that local data to gain any advantages from Rushmore.

As generally queried data is supossed to be a fairly small set (you would not bring tens of thousands of records from Oracle as that may not make sense), the gains you may have from Rushmore-optimizing your resulting cursor may be minimal. YMMV.