I left off being a database expert when the field mostly involved relational databases. My only guess here is that you can break the data down into smaller tables, and link the information through the keys. It isn't so much the number of rows (transport workers by SSN or similar identifier) that makes it complex, and it could be a fairly simple or manageable structure. I'm not sure what you mean by "lost code DBM architecture". You could do this sort of thing with Microsoft Access, but of course -- you're looking for an open source option. With Access, SQL Server and other options, I don't see why "open source" has to be a requirement.