A method is provided for simplifying maintenance of synchronicity between an active control system and a standby control system. As interdependent software modules on the active control system update stored state information in response to triggering events and actions, the transaction messages for dependent software modules are bundled together and sent to the standby control system as a single message. This avoids the problems that can arise when a switchover occurs when only some of the transactions messages from interdependent software modules have been transmitted before failure of the active control system.