Is there a paper / blog post / help entry on DR.DB?

I have questions.

Should I only have one DR.DB, or should I have one for each DF Project?

What defines when I need to update dr.db at a client site when I'm distributing reports?

Does the structure of DR.DB change over time with different versions of DR?

What kind of things does it store that are accessed at runtime?

How do I detect a mismatch between the DR.DB and the report set?