Redundancy

The WinCC OA SECS driver supports redundancy configurations to ensure continuous operation and reliability.

According to SEMI Standard E37, equipment typically does not support redundant connections to the host. However, the standard does not prohibit the implementation of redundancy, therefore both options are available when using the driver.

Redundancy Switch Scenarios

In the event of a redundancy switch, the behaviour of the connection depends on the Bit 0 of the “<_SecsConnection>.Config.Flags” DPE:

If “<_SecsConnection>.Config.Flags” Bit 0=0
  • The active connection is maintained.
  • Upon switch the passive side becomes active and establishes a connection.
  • The message queue is maintained only on the active side of the connection. Messages in the queue during the switch will be lost and should be resent by the new active host after the switch.
If “<_SecsConnection>.Config.Flags” Bit 0=1
  • Both sides attempt to connect, provided the equipment supports redundancy.
  • The message queue is maintained on both sides of the connection.
  • In case of a redundancy switch, the queue will be processed normally by the newly active host connection.