This document discusses different configurations for providing redundancy when using OPC (OLE for Process Control) servers and clients. It describes four common scenarios: 1) no redundancy with a single PLC, OPC server, and client; 2) redundancy on one computer with redundant PLCs and OPC servers; 3) networked redundancy across multiple computers with redundant PLCs, OPC servers, and DataHubs; 4) multiple client redundancy across networks with redundant PLCs, OPC servers, and multiple OPC clients connected via DataHubs.
2. No Redundancy
PLC OPC Server OPC Client
Process
? One process, one client
? Single data path (PLC and OPC server)
3. Redundancy ¨C one computer
Redundant PLCs Redundant OPC
Servers
DataHub OPC Client
Process configured for
redundancy
? One process, one client, one computer
? Redundant data paths
4. Networked Redundancy
Redundant OPC DataHubs for Network
Redundant PLCs
or
Servers tunnelling Internet
Process DataHub for OPC Client
tunnelling and
redundancy
? Redundant data paths
? 2 OPC server machines, 1 client machine
5. Multiple Client Redundancy
DataHub OPC Client
Redundant PLCs Redundant OPC DataHubs for
Servers tunnelling
Process
DataHub OPC Client
? Redundant data paths
? 2 OPC server machines, 2 client machines
6. Multiple Client Redundancy
DataHub OPC Client
Redundant PLCs Redundant OPC DataHubs for
Servers tunnelling
Process
DataHub OPC Client
? Redundant data paths
? 2 OPC server machines, 2 client machines