When you upgrade a piece of software on Linux, there are two paths it can go when there are incompatible changes in the config files (ok, 3 paths, Debian asks you what to do):
The "rpmnew" way: install the new config file as "whatever.rpmnew", which means the softwarewill break immediately, but that's ok, because you are doing upgrades, so you should be watching already.
The "rpmsave" way: replace the old file and save a copy as "whatever.rpmsave".
This has two problems:
The software may fail or not, or fail in a subtle way, and you will not notice right away.
Maybe the old file will be lost anyway:
lrwxrwxrwx 1 root root 32 jul 15 22:41 /etc/named.conf -> /var/named/chroot/etc/named.conf lrwxrwxrwx 1 root root 32 jul 15 22:36 /etc/named.conf.rpmsave -> /var/named/chroot/etc/named.conf
In this case the "file" was a symlink, so by "saving a copy" it only saved another symlink to the soon-to-be-overwritten file.
And that's why, ladies and gentlemen, the rpmnew way is the good way.