code: public void kill_zombie_appenders () {
     		//- Get all devices
      	Vector dl = Util.instance().get_device_list("*");
      	//- Check appenders validity then kill them if needed
  		for (Object aDl : dl)
  		{
  			//- Get device reference
  			DeviceImpl dev = (DeviceImpl) aDl;
  			//- Get device logger
  			Logger logger = dev.get_logger();
  			if (logger != null)
  			{
  				Enumeration all_appenders = logger.getAllAppenders();
  				while (all_appenders.hasMoreElements())
  				{
  					Appender appender = (Appender) all_appenders.nextElement();
  					if (((TangoAppender) appender).isValid() == false)
  					{
  						Util.out4.println("Removing zombie appender " + dev.get_name() + LOGGING_SEPARATOR + appender.getName());
  						logger.removeAppender(appender);
  					}
  				}
              }
          }
      }
docs: Kills zombie targets (i.e. appenders)