berkeley db and dba

Hi, I noticed that the ext/dba extension allows me to use Berkeley DB. I'm interested in using some of the newer features in Berkeley DB v4 (sleepycat's latest release). In particular, there are a set of features regarding a db environment. See http://www.sleepycat.com/docs/ref/env/intro.html for more information if you're interested. Basically the things that really attract me to this are the memory pools that might allow multiple apache processes to use shared memory (file-backed or system memory) for caching data. But the dba extension doesn't seem to provide any hooks for these calls, or other db-specific functions. What is the best way for me to get access to these functions? thanks dave viner