Hi BobSka and welcome to our forum!
You will have to write code to submit data from 2DS (secondary data source) to a DB. An alternative is to create main data source nodes for them and copy them. Not sure why you would want to save 2DS data. If it's save-worthy it should be in the main data source, no?
Patrick Halstead [InfoPath MVP]
InfoPathDev
Patrick Halstead
Project Manager at Qdabra