Can I use the RDBMS as an application server?
pjackson: I used to be an Enterprise architect for a Fortune 500  company. We did many of the things you are asking about. Here are my answers:1. Yes, you can. However, there will be tradeoffs. One important piece of sharing business logic involves sharing instances of running code, not just the logic itself. It's tough to implement a singleton in a set of stored procs. I'd recommend that you leave stored procs for the kinds of logic that you might code into a web service: transactional concerns that have a complicated set of steps.2. Yes, that's a popular approach, and for good reason: the objects you create against the persistence store are sharable at the instance level.3. It will scale less-well than an architecture with a solid middle tier, but it's impossible to put a user-count on it without knowing much much more. If you pick a commercial RDBS like Oracle or Sybase (and many people don't like to do that), you will find that there are a lot of expensive but effective scaling mechanisms to handle this. It's usually cheaper to invest in a decent middle tier, a caching server, and scale that way.4. That's not necessarily true. Portability is nice, but there are many other reasons to pull the business logic out of the database. For example, it's hard (but not impossible) to implement an event-driven system where transactions will fire off other business events downstream when you're using a stored procedure set as your logic layer. You can do it, but you end up with triggers or batch jobs that reduce the real-time processing capabilities of the whole architecture.5. P/L SQL is pretty powerful, but I still have my logic in objects rather than in Oracle. I can introduce caching and other sscaling strategies easier this way.Though I use and like Oracle, I'd steer you away from it unless you have a really good reason to buy it. It takes a lot more care-and-feeding than MySQL, the licensing model becomes oppressive when you start to need to cluster the DB, and experts in the area are expensive.Hibernate is a good framework. Why are you resisting the use of it? If you want to go heavy on the stored procedures, check out the iBatis framework. It's really good at ORM and stored procs.