db.0 corrupt - strange characters

Hi folks,

I've noticed a strange problem in my bind installation, my
/etc/bind/db.0 contains only strange characters, looks like binary data
or something similar.

I use debian packages, bind version 9.2.1.

Has anyone an idea what went wrong? The server is running since 40
days, the problem exists since 3 or max. 4 days.

best regards
Jens