code: @Override
      public String[] getDeviceList(final String serverName, final String className) throws DevFailed {
          final DeviceData send = new DeviceData();
          send.insert(new String[] { serverName, className });
          final DeviceData received = database.command_inout("DbGetDeviceList", send);
          return received.extractStringArray();
      }
docs: Get the list of device for a server and a class (execute DbGetDeviceList
  on DB device)
  
  @param serverName
  The server name
  @param className
  The class name
  @return
  @throws DevFailed