You can add FireBird (www.firebirdsql.org) to the database list. Mature open-source database, supports transactions (readers does not block writers), stored procedures, triggers, backup online etc. I have one app running in a hospital. It has 120 tables and over 2GB database. kinterbasdb provides DB API 2.0 to connects to it via python. Hope this helps Geraldo Lopes de Souza