[Zope] thread safety

Hi! I never wrote a multi threaded program and I don't know if my ZPublisher module is thread safe. I read http://www.zope.org:18200/Documentation/How-To/ThreadSafety, but this didn't help me much. I found no documentation to the Sync module. I'm not using ZODB or Databases, I'm storing the data in files and for faster access some data in a global dictonary with lists ({'1': {'1.1': ['a', 'b', 'c']}, '2': {'2.1': ...}). Are these operations thread safe or what could I do to make them thread safe? Oliver