If you do a fresh install, your database settings will be "printed" to your settings/siteaccess/[whatever]/site.ini.append.php

as long as you can only set a database connection in install process, why don't just set these values in settings/override/site.ini.append.php?

By the way, [FileSettings]/VarDir is set in settings/override/site.ini.append.php, so why not do the same for database?