[mikechops]

What you are doing should work. The *.rtm files contain the database info. I haven't made a lot of multi-million hand db's though. If the files get so big that they are larger than your available RAM then you may have problems.

When you rebuild a database for a site, you are prompted to ask whether you want to clear the database first. If you don't the hands will be added. You might encounter import speed problems if you don't have all the hands together in one folder. In particular, if the set of hands you are importing is older than the already imported hands, RT has to insert them into the middle of the db rather than just plonking them on the end. It wouldn't surprise me if it were quicker to just rebuild everything from the same folder. That way RT can sort the files by game number, importing oldest first and not have to do much insertion into the middle of the game number list.