I've started a thread in web/db, too...there are other problems, Janine Sisk e-mailed me a construct like this:
with_transaction { ... ns_db "begin/end transaction" ... }
Same problem wearing a different disguise.
Jin Choi sez they plan to have the Oracle driver spit out an error when it hits a begin within a transaction, in this case at least they'll catch the errors.
Anyway, I think the parameter-to-dp_process notion is a fine idea. Let's try to track aD on this one, I think there's a chance they'll adopt the same notion.