Testing db4o in bsh, with a view to using it in Freenet. We create a database, and write to it, and restart, it works. Then we deliberately fill up the disk (in another shell), and try to write to the database. db4o throws an Db4oIOException caused by out of disk space, but when we restart it, even if we remove the bigfile occupying all the disk space, we get an IncompatibleFileFormatException.

I have personally tried this with 6.4, a coworker tried it with 7.3, same result except different exception (IncompatibleFileFormat or InvalidSlot).

I know this is a case of deliberately breaking it to see if it still works ... but it ought to work, an embedded database included with an end-user application will frequently run up against temporary out of disk space conditions, it should recover gracefully (as Perst does for example).