code: @Override
    public void checkpoint(Result<Boolean> result)
    {
      if (! _journalStream.saveStart()) {
        result.ok(true);
        return;
      }
  
      TableWriterService readWrite = _table.getReadWrite();
      
      // long limit = Integer.MAX_VALUE; // 128
      int tailPid = _tailPid.get();
      for (int pid = 1; pid <= tailPid; pid++) {
        Page page = _pages.get(pid);
  
        if (page != null) {
          page.write(_table, this, readWrite);
        }
      }
  
      readWrite.fsync(new CheckpointResult(result));
    }
docs: Requests a checkpoint, flushing the in-memory data to disk.