Migrating SIMATIC PCS 7 from a Single OS to a Redundant Client-Server Project

Single-station operator stations (OS) work fine for small SIMATIC PCS 7 plants, but they cannot deliver the availability, scalability, and load distribution that production facilities require. This reference walks through the complete migration of an existing PCS 7 single-user ES/OS project into a redundant OS Server pair plus three OS Clients, covering PCS 7 V8.x and V9.x, with a parallel upgrade path for legacy V7.1 plants.

1. Target Architecture Overview

The migration target is a standard PCS 7 Client-Server configuration that follows the SIMATIC PCS 7 Minimal Configuration rules. The new architecture separates the engineering station (ES), the redundant OS Server pair (Master + Standby), and the OS Clients onto different PC Stations connected by a dedicated terminal bus.

Three network segments must be present and properly routed:

• Plant bus - connects the AS stations to the OS servers (typically Industrial Ethernet / PROFINET, isolated subnet).
• Terminal bus - connects the OS servers to the OS clients (standard TCP/IP Ethernet, switch-based, 1 Gbps recommended).
• ES engineering bus - carries ES-to-AS downloads, NetPro, and S7 connections; often shared with the terminal bus on the engineering NIC.

2. Prerequisites and Licensing

Before opening the project, validate that the existing ES, the new server pair, and the three clients all meet the PCS 7 hardware and software compatibility list (see SIMATIC PCS 7 V9.0 Released Modules and PCS 7 V8.2 Released Modules). Confirm the following:

3. Pre-Migration Inventory and Backup

Take a full backup of the ES before any change. PCS 7 projects are stored on the ES under the project path, typically C:\Program Files\Siemens\Automation\PCS7\S7Proj for V8.x and C:\ProgramData\Siemens\Automation\PCS7\<project> for V9.x.

1. Open the existing WinCC Explorer on the ES and run Project > Cross Reference. Export a list of all picture references, scripts, and tag connections for traceability.
2. In SIMATIC Manager (V8.x) or PCS 7 Plant View (V9.x), open Options > PCS 7 Plant Documentation and generate a PDF of the plant hierarchy (PH), the OS Area, and the network/NetPro configuration.
3. Use WinCC Explorer > Tools > Project Duplicator to create a full copy of the project on a separate drive. This is your rollback image.
4. Capture the WinCC archive path, alarm logging path, and report path. In V8.x these are configured under Computer > Properties > Graphics Runtime.
5. Record the S7 connections in NetPro: AS-OS connections use connection type "S7 Connection" and must be re-validated after the new server is online.

4. Step-by-Step Migration (PCS 7 V8.x / V9.x)

The migration runs in two phases: first the OS Server pair, then the OS Clients. Do not start the client phase until both servers are synchronized and the runtime is stable on the master.

4.1 Phase 1 - OS Server and Standby Configuration

1. Add the new PC Station for the Standby OS. In SIMATIC Manager, right-click the project and select Insert New Object > PC Station. Name it OS-Server-Stby (or the customer-specific hostname).
2. Insert the WinCC Application (Stby.). Open the new PC Station, right-click and choose Insert New Object > WinCC Application. Assign the Standby OS role (not "Server-Stby." - in V9.x this is renamed to OS Server (Stby.)).
3. Insert a CP if used. If the plant bus requires a hard real-time CP (e.g., CP 1623 or CP 1628), add the CP to the PC Station and assign it to the existing plant bus subnet. The terminal bus uses the standard Windows NIC and is assigned later.
4. Link the Standby to the Master OS. Open the properties dialog of the Standby OS, switch to the Target OS and Standby OS Computer tab, and enter the computer name of the existing target OS (now renamed to Master). This binding is what enables WinCC redundancy.
5. Run the Station Configuration Editor. On both the master and standby PCs, start Station Configuration Editor and assign the components to the indices declared in SIMATIC Manager (index 1 typically = WinCC Application, index 2 = CP, index 3 = additional OPC). Click Update Station and confirm the station name matches the SIMATIC Manager entry.
6. Configure AS-OS communication in NetPro. Open NetPro from SIMATIC Manager. For every AS in the project, check that the S7 connection to the OS still has a valid path through the plant bus. With redundancy, NetPro automatically generates the mirrored connection to the standby once the Standby OS is bound.
7. Convert the WinCC project to Multi-User. In WinCC Explorer on the master, choose Project > Properties and switch Project type from Single-User Project to Multi-User Project. Accept the prompt to generate the server data; this writes the package files the clients will later subscribe to.
8. Generate the server package. In the master project, right-click Server Data and select Generate Server Data. Repeat on the standby after the data has been replicated.
9. Download the PC Station to both servers. Highlight the new PC Station in SIMATIC Manager, then choose PLC > Download to Target Station > All. The Station Configuration Editor on each machine will instantiate the components and start the WinCC services.
10. Activate runtime and verify redundancy. Start WinCC Runtime on the master. Confirm that the standby logs "Partner Online" and the archive synchronization runs without errors. Pull the network cable from the master to confirm failover; restore only after the standby takes over.

4.2 Phase 2 - Terminal Bus and OS Clients

1. Create the Terminal Bus subnet. In NetPro, insert a new Ethernet subnet for the terminal bus. Assign a unique subnet ID and mask (e.g., 192.168.10.0/24). Do not overlap with the plant bus.
2. Add three new PC Stations for the clients. Insert OS-Client-01, OS-Client-02, and OS-Client-03. Each gets a single WinCC Application configured as OS Client. Bind each client to the terminal bus subnet through the Windows NIC.
3. Select the target OS server on each client. In the client's WinCC Application properties, enter the server computer name under Server Assignment. With redundancy, both master and standby are listed; the client automatically fails over when the active partner goes down.
4. Run the Station Configuration Editor on each client PC and load the project from SIMATIC Manager. The client only needs index 1 = WinCC Application; the terminal bus is the Windows NIC.
5. Generate the server package from the master one more time. The clients pull this package at startup; if the picture tree is missing tags, regenerate Server Data on the master and restart the client runtime.
6. Reference client (optional). If the three clients are identical, set up one of them as the Reference Client in WinCC Explorer. The other two inherit the same picture tree, user administration, and alarm routing. This simplifies change management.
7. Validate user rights through SIMATIC Logon. Confirm that operator, supervisor, and engineer roles propagate to the clients. Test logout on one client and login on another to validate the central user database.

5. Upgrade Path for Legacy V7.1 Projects

Plants still on PCS 7 V7.1 must be upgraded stepwise: V7.1 → V8.0 → V8.2 → V9.0 as the user reported. Each jump is a clean re-installation - PCS 7 does not support in-place upgrade between major versions. Plan downtime per upgrade.

After each upgrade, run PCS 7 OS Project Migrator to adapt the WinCC project to the new WinCC version, then redo the redundant server and client setup using the procedure in section 4.

6. NetPro and AS-OS Communication Configuration

NetPro is the central point where the redundant OS pair is bound to the S7 program. Two S7 connections per AS are now required - one to the master, one to the standby - and NetPro creates them automatically once both PC Stations are configured and the Standby OS is bound to the Master OS in the properties dialog.

7. WinCC Multi-User Project and Server Data

The conversion of a single-user WinCC project to multi-user is the single largest source of post-migration problems. Three things must happen in order:

1. The local tags (tags defined directly on the OS) are migrated to the server, but the picture tree still references them locally. The Generate Server Data step republishes them as server-side tags and rewrites the package.
2. Alarm logging and tag logging must be configured to write to the server's local disk, not the original ES path. Modify the archive paths in WinCC Explorer to point to D:\PCS7_Archives\ on the master and standby.
3. User administration moves from WinCC local users to SIMATIC Logon. Migrate existing users under Computer > User Administrator > Migrate and select the Logon domain.

8. Verification, Commissioning and Acceptance Tests

Document the following tests in the site acceptance protocol. Each test must pass before the redundant server pair is considered production-ready.

9. Troubleshooting Matrix

10. Operational Notes

• Always start the master first, then the standby. Reversed order results in a "Partner not yet defined" state until the master initializes.
• Avoid mixing the plant bus and terminal bus on the same physical NIC. Performance and broadcast storms will degrade picture update times below 1 s.
• Schedule archive round-up to occur during the standby's idle window. Round-up runs only on the active partner; a failover during round-up is safe but the standby completes the cycle.
• Keep the master and standby at the same Windows patch level. Asymmetric patches cause WinCC service restart loops after failover.
• Use the PCS 7 Maintenance Station if the plant requires a separate diagnostic OS - it runs as an additional client and does not consume AS-OS connection resources.

11. FAQ