This section details requirements to standardise redundancy across the MDIS interface. SPCS and DCS should be connected using two segregated communication channels. Designation of the primary communication channel between the SPCS and DCS shall be controlled at the DCS. Automatic reconnection / recovery in the event of a failed communication channel shall be implemented. Failure of either channel shall generate an alarm at the DCS. Communication configurations other than what is defined here may be used. However, it should be specified elsewhere and should be agreed between all parties prior to implementation. Additional redundancy options including physical and logical configuration should be based on required project availability.

In general, redundant communication between the SPCS and DCS shall:

  1. Facilitate active redundancy which enables a seamless transfer to a secondary controller in the event of a primary controller failure.
  2. Prevent or minimise the loss of subsea production due to a single-component failure or common-mode failure.

The information model available in MDIS OPC UA servers is affected by data arbitration choices (see 5.3.2).

OPC Redundancy is described in the following section.