code: private IoChannel getFileChannel(String fileName) throws IOException {
  		synchronized (prepareAnchor(fileName)) {
  			IoChannel fileChannel = openFiles.get(fileName);
  
  			if (fileChannel == null) {
  				File dbFile = fileName.equals(DEFAULT_LOG_FILE) ? new File(logDirectory, fileName)
  						: new File(dbDirectory, fileName);
  				fileChannel = IoAllocator.newIoChannel(dbFile);
  
  				openFiles.put(fileName, fileChannel);
  			}
  
  			return fileChannel;
  		}
  	}
docs: Returns the file channel for the specified filename. The file channel is
  stored in a map keyed on the filename. If the file is not open, then it
  is opened and the file channel is added to the map.
  
  @param fileName
  the specified filename
  
  @return the file channel associated with the open file.
  @throws IOException