Current configuration: Linux RH7.3 Zope 2.8.4 Python 2.4.2 (but the same is observed with Python 2.3.5) I continue to observe occasional failures of the Zope session variable mechanism. The problem manifests itself by a KeyError when accessing data in the session data container. We have recently moved to Zope 2.8.4 from Zope 2.7.6. The frequency of these errors aooears to have increased significantly; of late, we have occasionally seen error messages saying that an entire SESSION data container is missing. The session variable interface is very simple: a pair of Python Scripts, one that gets a session variable and another that sets it. Both use the copy-out/copy-in mechanism required for persistence. ## Script (Python) "getSessionVariable" ##bind container=container ##bind context=context ##bind namespace= ##bind script=script ##bind subpath=traverse_subpath ##parameters=varname ##title= ## request=container.REQUEST session=request['SESSION'] return session[varname] # Script (Python) "setSessionVariable" ##bind container=container ##bind context=context ##bind namespace= ##bind script=script ##bind subpath=traverse_subpath ##parameters=var, val ##title= ## request = container.REQUEST RESPONSE = request.RESPONSE session=request['SESSION'] session[var]=val request.set( 'SESSION', session ) Most of the information we store in session variables are simple numbers or strings. In a few instances, we store python lists, python tuples, or python dictionaries. I am beginning to suspect the source of my bug is a persistence problem perhaps triggered by a conflict error or garbage collection in the temporary store used to hold the session variables. I further suspect that lists and dictionaries stored in session variables need to be instances of PersistentDict and PersistentList and not ordinary python data structures. I'd appreciate confirmation on these two issues from someone who knows the persistence mechanism better than I. Neither PersistentDict nor PersistentList are exposed in the restricted namespace. Advice as to how to expose them would be helpful as well. If I have a complex data structure (a list of dictionaries) does all the substructure need to have persistence wrappers as well--that is, does it have to be turtles all the way down? Thanks in advance. -d