*             if the <code>MediatedFileChannel</code> cannot be created
     */
    synchronized FileChannel getFileChannel(long address) throws PersistitIOException {
        final long generation = address / _blockSize;
        FileChannel channel = _journalFileChannels.get(generation);
        if (channel == null) {
            try {
                channel = new MediatedFileChannel(addressToFile(address), "r");
                _journalFileChannels.put(generation, channel);
            } catch (IOException ioe) {
                throw new PersistitIOException(ioe);
            }
        }
        return channel;
    }