code: public synchronized void close() throws IOException {
          if (tmap == null) {
              throw new IllegalStateException("not open");
          }
          final RecordManager rm = tmap.getRecordManager();
          rm.close();
          tmap = null;
      }
docs: Closes the index.
  
  @throws IOException Thrown when one of the underlying I/O operations fail
  @throws IllegalStateException Thrown if {@link #open()} has not been
  invoked