Hi Leon,
MII workbench is a client to the Oracle database and here the Netweaver will also not come into picture as you are connection to the Oracle database through the driver you would have uploaded in the JDBC Drivers screen in MII.
Check the Oracle JDBC driver documentation to see if something is there.
Also I think this thing will be handled in the database itself. So you need to check Oracle database documentation also.
Regards,
Rohit Negi.