Comment by JdeBP

Text configuration in individual small files, described at length in the doco, merely compiled into a database for runtime use; just like /etc/pwd.db and /etc/spwd.db (compiled with pwd_mkdb from /etc/master.passwd) /usr/share/misc/termcap.db (compiled with cap_mkdb from /usr/share/misc/termcap) /usr/share/terminfo/?/* (compiled with tic) data.cdb (compiled with tinydns-data from data) nsd.db (compiled with zonec) /etc/postfix/virtual.db (compiled from /etc/postfix/virtual with postmap) and so on and so forth.