Abstract: There is disclosed a redundant process controller for use in a process facility having a plurality of process systems that produce process data, wherein the process data are gathered by process controllers associated with the process systems and are exchanged by the process controllers via a network. The redundant process controller is associated with a first selected process system and is capable of receiving process data from at least one remote process controller and intermittently transferring the received process data to the first selected process system.

Abstract: There is disclosed a system and method for maintaining data coherency between a primary process controller operable to execute process control tasks and a backup process controller operable to replace the primary process controller upon failure, wherein the primary process controller cyclically executes the process control tasks during base control cycles having a period, T. The system comprises 1) a tracking circuit operable to detect changed data in a main memory in the primary process controller; 2) a data buffer for temporarily storing the changed data; and 3) data transfer circuitry for transferring the changed data in the data buffer to a backup memory in the backup process controller at least once during each base control cycle of the primary process controller, such that the transfer of changed data does not interfere with execution of the process control tasks.