I am trying to establish a connection from ArcMap 10.0 -- Service Pack 5 to an Oracle DB (I thought it was 10g if might be 11g) on windows 7.. It is windows have connected to the database via Catalog. However, I keep getting an error when trying to add query layer. I have attached a picture for more context. Any ideas as to why? If I try to connect via oracle 11g it says failed to connect to the specified server. Underlying DBMS error.