code: public void merge(String parity, String source, String codecId, 
        int[] checksums) throws IOException {
      checkOpen();
      try {
        namenode.merge(parity, source, codecId, checksums);
      } catch (RemoteException re) {
        throw re.unwrapRemoteException(AccessControlException.class,
                                       NSQuotaExceededException.class,
                                       DSQuotaExceededException.class);
      }
    }
docs: Merge parity file and source file together into a raided file