@Override
  public void flush() throws IOException {
    if (!myMap.isClosed()) {
      //TODO RC: inefficiency: we do need to _store_ all cached data -- but we don't want to clear the cache!
      //         With current implementation we get empty cache every time the flush() is called.
      clearCachedMappings();
      if (myMap.isDirty()) myMap.force();
    }
  }
@Override
  public void flush()