[Zope] - What constitutes a transaction?

[Ty Sarna]

I'm obviosuly missing something here.

I have a product, a subclass of Folder.  It has several methods that do
things to its internal state.  Some of these methods cause a transacton
to be generated (Ie, when adding or deleting objects, setting
properties, etc., the method shows up in Undo).  When I shut down zope
and restart it, these changes are still there. My added methods have
effect that is forgotten at shutdown, and they don't show up in the Undo
list. I have another Product where my added methods do work correctly.

What am I missing?