private DataTree convertThisSnapShot() throws IOException {
    // create a datatree
    DataTree dataTree = new DataTree();
    DataNodeV1 oldDataNode = oldDataTree.getNode("");
    if (oldDataNode == null) {
      // should never happen
      LOG.error("Upgrading from an empty snapshot.");
    }

    recurseThroughDataTree(dataTree, "");
    dataTree.lastProcessedZxid = oldDataTree.lastProcessedZxid;
    return dataTree;
  }
 /**
  * the last processed zxid in the datatree
  *
  * @param zxid the last processed zxid in the datatree
  */
 public void setlastProcessedZxid(long zxid) {
   dataTree.lastProcessedZxid = zxid;
 }