Forum OpenACS Q&A: Re: Server melting down
Presumably a connection thread ends up spending a large fraction of its time feeding content back to a slow modem user over TCP/IP, and the thread is not holding a database handle during that time (well, as long as you haven't botched your Tcl programming it's not). So it seems reasonable that most people use a number of threads substantially larger than their number of db handles.
I suspect an Oracle connection is also pretty heavyweight, so you are probably sucking up lots of RAM for no good reason in database connections which you never use. Hopefully it will all just be swapped out most of the time, of course.
But all that is just my supposition. Some kind of nice Linux, AOLserver, Oracle, PostgreSQL, and OpenACS performance test suite, and good repeatable results from it, would be nice to have. :)