Hi, Is transaction build in of ZODB? I have a product which keep a counter property and a inc method which will increase the property with a integer amount. I would like to make sure that concurrent inc call will not cause problem. Is ZODB automatically do transaction and prevent corrupt of data? My class is like this: class Cid( OFS.SimpleItem.Item, # A simple Principia object. Not Folderish. Persistent, # Make us persistent. Yaah! Acquisition.Implicit, # Uh, whatever. AccessControl.Role.RoleManager # Security manager. ): """Cid object. Keep an integer value and provide an way to inc it. """ meta_type = 'Cid' # what do people think they're adding? manage_options = ( # what management options are there? {'label': 'Edit', 'action': 'manage_main'}, {'label': 'View', 'action': ''}, # defaults to index_html {'label': 'Security', 'action': 'manage_access'}, ) __ac_permissions__=( # what permissions make sense for us? ('View management screens', ('manage_tabs','manage_main')), ('Change permissions', ('manage_access',) ), ('Change Cid' , ('manage_edit',) ), ('View Cid', ('',) ), ) def __init__(self, id, title='', initval=0): """initialise a new instance""" self.id = id self.title = title try: self.counter = int(initval) except: self.counter= 0 def inc(self, increment=1): """ inc counter """ self.counter = self.counter+increment return def __repr__(self): '''aa''' return self.counter def __str__(self): ''' a ''' return str(self.counter) def index_html(self): ''' return data ''' return self.counter manage_main = HTMLFile('CidEdit', globals()) # Management Interface def manage_edit(self, title, counter, REQUEST=None): """does this really need a doc string?""" self.title = title try: self.counter = int(counter) except: pass if REQUEST is not None: return MessageDialog( title = 'Edited', message = "Properties for %s changed." % self.id, action = './manage_main', ) I add an object aaa of Cid and make the following call on dtml: <dtml-call "aaa.inc()"> Counter is now : <dtml-var aaa> How could I prevent aaa get updated after inc() is call? Rgs, Kent Sin --------------------------------- kentsin.weblogs.com kentsin.imeme.net