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Configuring WinCC as an OPC DA Server for Third-Party Systems in Redundant PCS 7 Environments

Configuring WinCC as an OPC DA Server for Third-Party Systems in Redundant PCS 7 Environments

In SIMATIC PCS 7 (V6.1 through V9.x), WinCC acts natively as an OPC DA Server (OPCServer.WinCC), allowing third-party OPC clients (such as Matrikon OPC) to read and write process variables. In redundant OS Server environments, third-party clients must either support OPC Server Redundancy (via redundancy brokers like Matrikon ORB) or connect via the Siemens OpenPCS 7 station, which provides an automated single-point failover interface.

Table of Contents

WinCC OPC Architecture: Server vs. Client Roles

In process control integration, external manufacturing execution systems (MES), enterprise historians, or laboratory information management systems (LIMS) frequently need to stream real-time process data from SIMATIC PCS 7.

Commissioning engineers often experience confusion regarding the roles of WinCC and testing tools:
* WinCC Runtime as OPC DA Server: Whenever WinCC Runtime activates, it automatically launches its native OPC DA Server component: OPCServer.WinCC (or OPCServer.WinCC.1). It exposes all internal and external process tags, alarms, and historical archives to external applications.
* OPC Scout: A diagnostic OPC test client provided by Siemens to browse and read local or remote OPC servers. It cannot serve tags to external third parties; it merely verifies that OPCServer.WinCC is operational locally.
* The Integration Goal: To transfer tags to a third-party application (such as Matrikon OPC Data Manager or Wonderware/Kepware), the third-party application must connect as an OPC Client directly to OPCServer.WinCC over the network.

Handling Server Redundancy for External OPC Clients

In redundant SIMATIC PCS 7 OS architectures (Server 1 and Server 2 running WinCC Redundancy), establishing external OPC connections introduces a high-availability challenge:

  1. Independent Server Instances:
    * Server 1 hosts OPCServer.WinCC pointing to its local project database.
    * Server 2 hosts an identical OPCServer.WinCC pointing to its redundant database.
    * Neither instance automatically redirects external client connections if its host PC fails or reboots.

  2. The Single-Client Connection Failure:
    * If a third-party OPC client connects solely to Server 1's IP address and Server 1 is rebooted for maintenance, the third-party connection drops completely, even though Server 2 is actively operating the plant.

  3. High-Availability Integration Solutions:
    * Solution A: Deploy SIMATIC OpenPCS 7 (Siemens Recommended):

    • OpenPCS 7 is an official PCS 7 add-on station that connects to both OS Server 1 and Server 2.
    • It provides a unified, redundant OPC DA, OPC HDA (historical data), and OPC A&E (alarms) server interface. If the active server fails, OpenPCS 7 executes bumpless automatic switchover to the partner server without disconnecting the external client.
    • Solution B: Deploy Third-Party Redundancy Middleware (Matrikon ORB):
    • Install Matrikon OPC Redundancy Broker (ORB) on the client PC. ORB maintains active connections to both Server 1 and Server 2, monitoring server heartbeat and switching data streams automatically.

Step-by-Step Configuration and DCOM Security Setup

1. Verify Local OPC Server Operation with OPC Scout

  1. On WinCC OS Server 1, activate WinCC Runtime.
  2. Launch SIMATIC NET OPC Scout (Start > Siemens Automation > SIMATIC NET > OPC Scout).
  3. Expand Local COM Server > OPC.WinCC.
  4. Double-click the server to connect; browse Tag Management and add a test process tag.
  5. Confirm OPC Scout displays the tag value updating with quality code good (0xC0).

2. Configure Windows Security and DCOM on WinCC Server

  1. Ensure both the WinCC Server and the third-party client PC reside in the same Windows Domain or share an identical local user account with identical passwords.
  2. On the WinCC Server, press Win + R, type dcomcnfg, and press Enter.
  3. Navigate to Component Services > Computers > My Computer.
  4. Right-click My Computer > Properties > COM Security:
    * In Access Permissions > Edit Limits...: Grant Remote Access to ANONYMOUS LOGON, Everyone, and Interactive.
    * In Launch and Activation Permissions > Edit Limits...: Grant Remote Launch and Remote Activation to Everyone and Interactive.
  5. Under DCOM Config, locate OPCServer.WinCC:
    * Right-click Properties > Identity: Select The Interactive User (or specify the dedicated shared service account).

3. Configure the Third-Party OPC Client

  1. On the third-party computer, open your OPC client software (e.g. Matrikon OPC Explorer).
  2. Specify the remote node: enter the IP address or NetBIOS name of WinCC Server 1.
  3. Select server identifier: OPCServer.WinCC.
  4. Connect to the server; browse the WinCC Tag Management hierarchy.
  5. Select the required process tags and establish cyclic subscription (e.g. 1000 ms update rate).

External OPC Integration Topologies Matrix

Integration TopologyArchitecture ComponentsRedundant Failover?Network ProtocolSoftware License RequiredDirect OS Server ConnectionThird-party client connects directly to Server 1NO (Manual reconnect if Server 1 halts)Microsoft DCOM / RPCStandard WinCC Server (Included)OpenPCS 7 StationDedicated OpenPCS 7 PC bridging redundant serversYES (Automated bumpless failover)DCOM or OPC UASIMATIC PCS 7 OpenPCS 7 licenseMatrikon Redundancy BrokerThird-party client running Matrikon ORBYES (Client-side automatic switchover)DCOM / SocketsMatrikon commercial licenseWinCC OPC UA Server (V7.3+)Modern WinCC OPC UA Server endpointPartial (Client-managed UA reconnect)Pure TCP/IP (opc.tcp://)Standard WinCC (Included in V7.3+)

Verification

  1. In the third-party OPC client, verify the connection status to OPCServer.WinCC reports Connected.
  2. Subscribe to 10 analog process tags (e.g. pressure and temperature transmitters).
  3. Confirm values update cyclically with Quality Code 16#C0 / Good.
  4. Invert a digital bit in CFC on the AS; verify the state change reflects on the third-party client within 1 second.
  5. If using OpenPCS 7 or redundancy middleware, disconnect the primary server network cable; confirm communication fails over to the partner server without losing data.

Limitations and Operational Precautions

  • Avoid High-Frequency Polling via DCOM: Polling thousands of tags at sub-100 ms intervals over DCOM saturates WinCC CPU resources. Use exception-based reporting (Unsolicited / On-Change) or aggregate subscriptions to 1000 ms.
  • Firewall Port Openings: DCOM requires TCP Port 135 and dynamic ephemeral ports (49152 to 65535) open between the third-party PC and the WinCC Server.
  • OpenPCS 7 Licensing Notice: When deploying OpenPCS 7 for redundant supervisory integration, verify order numbers (e.g. MLFB 6ES7658-0XX18-0YB0) and client access limits against the Siemens ST PCS 7 catalog with an authorized distributor.

Engineer FAQ

Can I use OPC Scout to send tags to another PC?

No. OPC Scout is purely a client for viewing and diagnosing local or remote OPC servers; it has no server functionality to forward tags.

Does WinCC V6.0 support OPC Unified Architecture (OPC UA)?

No. Native OPC UA Server functionality was introduced in SIMATIC WinCC V7.0 SP3 / V7.2 and PCS 7 V8.0. WinCC V6.0 supports only OPC DA Classic (over DCOM).

Why does the remote OPC client fail with 'Access Denied 0x80070005'?

This is a classic DCOM permissions error. The user account logged into the client PC does not exist on the WinCC Server, or the DCOM Access Limits in dcomcnfg lack remote permissions for that user.

Technical References

Related Articles

Related Tags

  • OPC DA
  • WinCC OPC Server
  • OpenPCS 7
  • Matrikon
  • DCOM
  • PCS 7 V6.1
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