I'd been playing with Oracle's handy external file datatype BFILE and was planning to post a note on them. Then I remembered that Harry Fuecks had already been there with style.
Instead I'll just point out a note that Lukas Smith alerted me to. A while back OTN published an article by Tobias Schlitt on the MDB2 database abstraction layer. Since then there were a few small changes to MDB2 and it has now gone "stable". These three points augment the article and will be helpful to MDB2 users.