I know you don’t want to use Java but I believe you could setup the JDBC driver and use RPG ILE api’s to access it. And have the JDBC driver on your external computers. We are currently looking at that now but have not went any further than discovery.
It isn’t the opposite of ODBC. It’s the same thing as ODBC. The same requirement exists and the same solution applies.
Go to the database vendor — Oracle/Sybase/Informix — and ask them how you can obtain the appropriate driver. Be prepared to pay through the nose, of course. Remote access drivers are always the responsibility of the database vendor. That’s why IBM is responsible for supplying ODBC to access DB2.
Or use JDBC or DRDA (if supported by the vendor; ODBC is a modified subset of DRDA).