[BBLISA] Definition of dump levels?

[Scott Ehrlich]

I've seen so many references to dump levels, but none of them, including the 
man page, actually says what, specifically, each level covers.

For example, a level 0 would presumably back up everything.  But will it still 
do so if I perform a level 0 today, update /etc/dumpdates, then perform another 
level 0 just after, and no files have changed?

What about the other levels?  What do they do?

Thanks.

Scott