[Zope] Concurrency control

Guten Abend. According to the Zope Developer's Guide our favourite web application server prevents dirty reads with his transaction support. Is it possible to prevent non-repeatable reads and phantom reads, too? Or should I use a more appropriate tool like PostgreSQL with support for MVCC? Is there more documentation about Zope's transaction support? (Or is it another case for "Read the source, Luke"?) Cheers, Nils