code: public int getPersistentVersion()
    {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
      {
        SibTr.entry(tc, "getPersistentVersion");
        SibTr.exit(tc, "getPersistentVersion", new Integer(DEFAULT_PERSISTENT_VERSION));
      }
  
      return DEFAULT_PERSISTENT_VERSION;
    }
docs: Return the class version number when the MessageStore wants to persist
  the object.  Each class will have its own version number.  Any
  time the data persisted is changed, this version will have to be
  incremented so that the restore routine can distinguish between old and
  new objects and act accordingly.