Hi ,
Another point for future (OE12), SSJ will not work for a request on several DB , it could have a huge impact on performance.
Tom and Rob are correct , managing multiple Db could be harder than a single DB.
I am responsible for over 10K hosted databases for my clients, all of them have several DB (more than 15 DB).
There is no "magic parameter" , each DB should have its set of parameter, you should set them individually, (if a memory consumption increase for a DB , you should decrease it on another DB). Tuning thoses parameter is "funny" game ...
It is feasable but it tooks times.
I join a picture of my activity of the previuos week, it is an uncomplete summary, some tasks are missing .
More Db means more time to do the tasks.
Patrice