Redundancy

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Redundancy connections to controllers will prevent data loss in case of connection interrupting.

A controller needs to have two network adapters. The computer need to have two network adapters, too.

For redundancy connections two or three sets of connection parameters will be defined.

At runtime all connections will be established. One will be master, this will handle the data.

The second connection will be the reserve. Its status will be checked only.

There are some options for the redundancy:

•	Check the connection for running

•	Check the controller run status

•	Check a watchdog element for periodically changes

In case of interrupting the master all elements will be switched to the slave.

This will work transparently to the OPC application. The items don't deliver errors.

Over OPC the status of both connections can be checked. Details here.

Technical Details

There are two modes of operation

•	Dynamic master One connection becomes the master. If it breaks down another connection becomes the master

•	The first connection is master always. If it breaks down a slave will handle the data. If the master connection is available again it becomes master again.

For testing purposes the active connection can be switched by the OPC client.

•	Dynamic master The connection switched to becomes the master

•	Static master It will be switched to the slave. After one minute it will be switched back to the master if it will work.

Hints:

•	Redundancy connections can not be simulated.

•	Redundancy connections do not become suspended it no item uses them.

•	Each single connection of the redundancies will use one connection from the licensed pool.

•	The controllers used in a redundancy connection needs to be from the same family.