Usually, each thread has its own data to minimize interference and to localize synchonization in the transaction commit. However, this makes it difficult to control such data from a single point. E.g. it is very difficult to invalidate cache entries: while there is no problem for a thread to invalidate entries in its own cache, it is very difficult to do the same with the corresponding caches in the other threads. 'Shared Resource' is a module that manages resources shared by all threads. Such resources can be controlled much more easily. A shared resource provides locking capabilities (via Python's RLock) and performs automatic locking for function calls. Access to non-functions is not protected. More information and download: URL:http://www.dieter.handshake.de/pyprojects/zope/SharedResource.html Dieter