Hello, I try to create a counter of which I am certain that it sends back in every Call a different result. I should so manage concurent acces on this one. The following method is not valid I have to look for a product which could make works: ---- ID = context.nextID context.manage_changeProperties( { 'nextID' : ID+1 } ) ---- But products found (FSCounter and to threadSafeCounter) uses the File System to manage the concurrent access on the counter value. I want to use the method described in the article " Advanced ZODB for python Programmers " ( Http://www.zope.org/Documentation/Articles/ZODB2) by creating a product based on the following code: ------------ class Counter(Persistent): self.count = 0 def hit(self): self.count = self.count + 1 return self.count def _p_resolveConflict(self, oldState, savedState, newState): # Figure out how each state is different: savedDiff= savedState['count'] - oldState['count'] newDiff= newState['count']- oldState['count'] # Apply both sets of changes to old state: return oldState['count'] + savedDiff + newDiff ---------- Is the class "Persistent" assure the value " self.count " to be not identical in two simultaneous calls of the "hit" method (not identical return value)? -- Yann Lugrin yann.lugrin@gmproject.net