code: @Override public void onAck() {
      // remove local cache but NOT in case it is already on disk
      // (ie memory can be reclaimed and we assume we have plenty of disk space)
      if( _dontCache && !_xval.isPersisted() ) H2O.putIfMatch(_xkey, null, _xval);
      if( _xval != null ) _xval.completeRemotePut();
    }
docs: Received an ACK