code: public void flush() {
      lock.writeLock().lock();
      try {
        OMMapBufferEntry entry;
        for (Iterator<OMMapBufferEntry> it = bufferPoolLRU.iterator(); it.hasNext();) {
          entry = it.next();
          if (entry.file != null && entry.file.isClosed()) {
            if (removeEntry(entry))
              it.remove();
          }
        }
      } finally {
        lock.writeLock().unlock();
      }
    }
docs: Flushes away all the buffers of closed files. This frees the memory.