If you haven't read it yet, there is a book being like the Bible to all OpenACS users. It's Philip Greenspun's 'Philip and Alex Guide to Web Publishing'. You may download it at
http://www.arsdigita.com/books/panda. I think you will find much information, not only about the db connectivity, but developing web applications with Tcl as well.
Philip has written two other books, 'Tcl for Web Nerds' and 'SQL for Web Nerds', and they also are available for download at http://www.arsdigita.com/books/tcl and http://www.arsdigita.com/books/sql. You may also want to check AOLServer documentation at http://aolserver.com/docs.
