BE2012: What happens when catalog files are deleted/truncated?

I have found some vague answers to my question in other articles, but I would like a clear answer before I proceed with deleting 4 years worth of catalog files. What happens when the catalog files for a particular piece of media are deleted or truncated? Does the media server:

A) retain the allocated and/or modified date of media, but media must be cataloged before data can be restored from it?

-OR-

B) treat any media without corresponding catalog files as Foreign Media, as though the media server had never seen it before?

Thanks.