code: public void flush() throws JournalException
      {
      	if (failing)
      		throw new JournalException("Store journal is failing");
      	
      	boolean newFlushRequired = false;
      	synchronized (journalWriteQueue)
          {
      		if (unflushedJournalSize > maxUnflushedJournalSize)
      		{
      			newFlushRequired = !flushingJournal;
      			if (newFlushRequired)
      				flushingJournal = true;
      			unflushedJournalSize = 0;
      		}
          }
      	
      	// Flush journal to store (asynchronous)
      	if (newFlushRequired)
          {
          	try
          	{
          		asyncTaskManager.execute(flushJournalAsyncTask);
          	}
          	catch (JMSException e)
          	{
          		throw new JournalException("Cannot flush journal asynchronously : "+e);
          	}
          }
      }
docs: Flush the journal write queue (asynchronous)