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Migrating from Single Station ES-OS to Redundant OS Servers in SIMATIC PCS 7 - Licensing and Topology Rules

Migrating from Single Station ES-OS to Redundant OS Servers in SIMATIC PCS 7 - Licensing and Topology Rules

Migrating an existing SIMATIC PCS 7 v8.1 single-user Engineering and Operator Station (ES/OS Single Station) to a high-availability redundant server architecture cannot be achieved by simply duplicating the Single Station runtime license. According to Siemens PCS 7 licensing rules, redundant server pairs strictly require two identical WinCC Server Runtime licenses, two identical Process Object (PO) runtime licenses, and the WinCC Redundancy license package on each server. The most cost-effective and architecturally sound upgrade path retains the existing IPC as an Engineering Station and OS Client (or Maintenance Station), while deploying a new, dedicated redundant server pair for 24/7 continuous process monitoring.

Table of Contents

Architectural Limitations of PCS 7 Single Stations

In compact industrial automation plants, SIMATIC PCS 7 is often initially deployed as a Single Station (ES/OS):
- A single industrial PC (IPC) hosts both the engineering environment (SIMATIC Manager, CFC, SFC) and the runtime operation (WinCC OS).
- The station connects directly to the S7-400 plant bus and controls process visualization locally.

As facilities expand, operational risks multiply:
1. Single Point of Failure: Hardware failure, hard disk crash, or OS freeze on the single IPC halts plant visualization and alarm logging completely.
2. Maintenance Contention: Editing CFC charts, running full compilations, or performing backups consumes CPU and memory, degrading real-time operator responsiveness.
3. Client Inability: A PCS 7 Single Station cannot serve multi-client architectures or support distributed control rooms without migrating to a server-based topology.

Siemens Minimal Configurations vs Client-Server Topologies

When planning an expansion, two potential topologies exist in Siemens documentation:

Approach A: PCS 7 Minimal Configuration (Redundant Single Stations)

  • Documented in Siemens Application Example (Entry ID: 24023824).
  • Consists of two single stations configured as redundancy partners without dedicated servers.
  • Limitation: Highly restrictive; cannot connect standard OS Clients, severely limits asset management, and requires complex station synchronization rules. Not recommended for plants planning future multi-client expansions.

Approach B: Standard Client-Server Redundancy Architecture

  • Consists of a dedicated Redundant OS Server Pair (OS Server 1 and OS Server 2) communicating with the plant bus.
  • The existing IPC is repurposed as a dedicated Engineering Station (ES) and OS Client.
  • Advantage: Completely decouples process control from engineering modifications, allows adding up to 32 OS Clients or Web Clients, and provides bumpless failover.

Licensing Requirements for Redundant OS Servers

Upgrading to redundant servers requires specific Siemens commercial licenses:

[!IMPORTANT]
When procuring OS licenses, always validate final license quantities and MLFBs against the applicable Siemens catalog and authorized distributor quotation. Redundant configurations require separate identical licenses for each server.

  1. OS Server 1 (Master):
    - WinCC Server Runtime License (e.g., 6AV6381-...).
    - WinCC Process Object (PO) License (matching plant tag count).
    - WinCC Redundancy Option License (6AV6371-1CF07-0AX0).
  2. OS Server 2 (Standby):
    - Identical WinCC Server Runtime License.
    - Identical WinCC Process Object (PO) License.
    - WinCC Redundancy Option License (6AV6371-1CF07-0AX0).
  3. Engineering Station / OS Client:
    - Standard PCS 7 Engineering License (retained from original single station).
    - WinCC OS Client Runtime License (e.g., 6AV6381-...) to allow the ES to view the plant as an operator console.

Recommended Migration Topology: ES/OS Client and Redundant Servers

The diagram below illustrates the industry-standard migration target:

+-----------------------------------------------------------------+
|                       TERMINAL BUS (ETHERNET)                   |
+-----------------------------------------------------------------+
        |                                       |            |
        v                                       v            v
+------------------+                   +------------------+  +------------------+
|    ES / CLIENT   |                   |   OS SERVER 1    |  |   OS SERVER 2    |
| - SIMATIC Manager|                   |   (Master)       |  |   (Standby)      |
| - WinCC Client RT|                   | - WinCC Srv RT   |  | - WinCC Srv RT   |
+------------------+                   | - WinCC Redund.  |  | - WinCC Redund.  |
                                       +------------------+  +------------------+
                                                |                     |
                                                +----------+----------+
                                                           | (Sync Cable)
                                                           v
+-----------------------------------------------------------------+
|                         PLANT BUS (ETHERNET)                    |
+-----------------------------------------------------------------+
                                |
                                v
                     [ S7-400 / CPU 410-5H ]

The ES operates as a client station. If the engineer needs to perform system modifications, deactivating runtime on the ES client does not affect plant visualization on the servers or other clients.

Comparative Architecture Matrix: OS Expansion Pathways

The table below compares the upgrade pathways:

ArchitectureHardware RequiredRedundancy MechanismClient ScalabilityLong-Term ViabilityRetain Single ES/OS0 new PCsNone (Single Point of Failure)0 ClientsPoor (High operational risk)Minimal Config (Dual Single)1 new PCRedundant Single Station0 ClientsLow (Restricted feature set)Redundant Server + ES Client2 new Server IPCsNative WinCC RedundancyUp to 32 ClientsRecommended Industry Standard

Step-by-Step Procedure: Reconfiguring SIMATIC Manager for Redundant Servers

Execute the following procedure on the Engineering Station:

Step 1: Reconfigure Hardware in SIMATIC Manager

  1. In SIMATIC Manager, open the project in Component View.
  2. Insert two new PC Stations: OS_SRV1 and OS_SRV2.
  3. In HW Config for OS_SRV1:
    - Insert WinCC Appl. in Slot 1.
    - Insert network adapters (IE General or CP 1623) for Plant Bus and Terminal Bus.
  4. In HW Config for OS_SRV2:
    - Insert WinCC Appl. stby in Slot 1.
    - Insert identical network adapters.
  5. In SIMATIC Manager, link OS_SRV2 as the Redundant Partner in OS_SRV1 properties.

Step 2: Convert Existing Single Station to OS Client

  1. In HW Config of the existing IPC station, change the application type from WinCC Appl. to WinCC Client Appl..
  2. Save and compile HW Config.

Step 3: Compile NetPro and Generate Server Packages

  1. Open NetPro; configure S7 Named Connections from both OS_SRV1 and OS_SRV2 to the S7-400 CPUs.
  2. Perform full OS Compilation targeting OS_SRV1.
  3. Generate server packages (.pck) on OS_SRV1 and load the package into the OS Client project.
  4. Download the runtime projects to both servers and the client.

Verification

To confirm that the redundant server architecture is operational:
1. Redundancy Health Check: On OS Server 1, inspect internal WinCC tag @RM_MASTER (value 1) and @RedundancyState (value 1 - synchronized).
2. Client Connectivity: On the ES/Client station, launch WinCC Runtime; verify that process graphics display live data fed from Server 1.
3. Failover Audit: Disconnect the plant bus network cable from Server 1; verify that Server 2 transitions seamlessly to Master (@RM_MASTER = 1) and the client switches data providers without process interruption.

Limitations and Operational Precautions

Engineering teams must observe the following precautions:
- For redundant OS systems, explicitly verify the licensing requirement for each server; never assume a single license key covers both server nodes.
- When using servers as operator stations (Server-Client mode), connect no more than 2-3 external clients; running heavy client graphics directly on server consoles consumes processing power required for alarm archiving.
- Ensure the dedicated redundancy synchronization link between Server 1 and Server 2 utilizes a separate physical cable (crossover or dedicated switch) isolated from terminal bus traffic.

Engineer FAQ

Can I reuse my existing Single Station OS license on one of the new servers?

No. A WinCC Single Station Runtime license is commercially and functionally distinct from a WinCC Server Runtime license. A server requires the WinCC Server RT package and Redundancy option.

What happens to existing historical tag data during the migration?

Historical archives from the single station can be copied and attached to OS Server 1 using the WinCC Archive Connector or SQL Server Management Studio before starting runtime.

Can the ES station also serve as an active operator station in an emergency?

Yes. When configured as an OS Client, the ES station provides complete operator control and monitoring identical to dedicated control room client stations.

Technical References

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Related Tags

  • WinCC Redundancy
  • Single Station
  • OS Server
  • OS Client
  • Licensing
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