code: public final void start() throws IOException {
          initialiseOffsets();
  
          dataFileBuffer = byteBufferFactory.build(getBufferLength());
          synchronized (globalLock) {
              populateDataBuffer(dataFileBuffer, metricData.values());
              preparePerMetricBufferSlices();
          }
  
          started = true;
      }
docs: /*
  (non-Javadoc)
  @see io.pcp.parfait.pcp.PcpWriter#start()