I have the following setup (unrelated lines are omitted): class Deliverer(Folder): def manage_afterAdd(self, item, container): if item is self: self.__ac_local_roles__ = dr_localroles(self) class dr_localroles(Persistent): def __init__(self, dr): self.dr = dr dr_localroles implements a few methods of the dictionary interface, so I can always check the effective settings via the Security/local roles zmi page. In order to computing roles, dr_localroles requires its parent object instance (Deliverer), that's why I store a reference to it as an attribute. Question: - Is there a way for dr_localroles to refer its parent without holding a reference to it or using weak reference? - Is there an equivalent of sys.getrefcount for ZODB persistent objects? Also a note for the archives: I wanted to make sure that if I delete a Deliverer object, it will indeed be removed from ZODB. For this I got the oid of the object, deleted it and than tried to get it back via the oid. The trick is, that you'll only get a POSKeyError if you pack the database and flush the cache. This latter one was not obvious for me. Reagards, Sandor