Architectural Role and Operational Mechanics of WinCC Application Reference Stations in PCS 7

A WinCC Application Reference ('WinCC Appl. (ref)') in SIMATIC PCS 7 is an architectural mechanism that allows multiple physical PC stations to execute a shared Operator Station project without creating separate project databases in SIMATIC Manager. In this configuration, a single 'Base OS' holds the graphics, tag management, and script configuration; the Reference OS inherits these files during download while automatically adapting its internal computer name. Crucially, deploying a Reference OS reduces engineering compilation effort, but does not reduce runtime licensing: each physical station running a Reference OS mandates its own independent WinCC Runtime and Process Object license packages validated through an authorized Siemens distributor quotation.

Executive Summary

Optimizing engineering efficiency in distributed control systems requires minimizing redundant configuration across operator consoles. In control rooms featuring multiple identical operator clients or redundant single-station architectures, configuring distinct WinCC projects for each station introduces synchronization overhead and risks operational discrepancies. SIMATIC PCS 7 incorporates the WinCC Application Reference to enforce configuration uniformity. While this structure centralizes engineering, practitioners often hold misconceptions regarding its operational autonomy and software licensing entitlements. This article analyzes the architectural mechanics of Reference OS deployments, clarifies communication and redundancy behaviors, and details commercial licensing guardrails.

Architecture and Fundamental Mechanics

Reference OS Architecture, Runtime Data Separation, and Commercial Licensing Guardrails:

Architectural Differences: Independent OS vs. Reference OS vs. OS Client:
Independent OS (WinCC Application): Has its own project container, requires independent compilation, and maintains unique screen hierarchies and tag tables.
Reference OS (WinCC Appl. (ref)): Points to an existing Base OS. When downloaded, it creates an independent runtime database on the target station containing an exact clone of the Base OS, but configured with the reference machine's computer name.
OS Client (WinCC Application Client): Does not poll controllers directly; connects to OS Servers over the Terminal Bus and loads server data packages (.pck).
Runtime Autonomy of the Reference Station:
Once downloaded, a station hosting a WinCC Appl. (ref) operates completely autonomously.
It runs its own local Microsoft SQL Server runtime instance, executes its own local communication channel drivers to the AS controllers over the Plant Bus, and maintains its own local alarms and tag archives.
If the Base OS station is powered down or disconnected, the Reference OS continues monitoring and controlling the plant without interruption.
Commercial and Licensing Accuracy Guardrails:
A common misconception is that using WinCC Appl. (ref) shares or waives software runtime licenses.
Each physical PC running a Reference OS requires separate, full runtime licensing:
1. SIMATIC WinCC Runtime license matching the required Process Object (PO) count (e.g. 500 PO, 2000 PO).
2. WinCC Redundancy license if operating as a redundant OS Single Station pair.
3. Separate licenses for optional packages (e.g. BATCH, Route Control, WebNavigator).
Engineering efficiency is gained in compilation time, not in software license quantities. Validate all procurement lists with an authorized Siemens distributor quotation.

Step-by-Step Implementation Procedure

Determine System Architecture (Single Station Redundancy vs Client Pool):
* Assess whether the target stations require direct Plant Bus controller polling (OS Single Station) or server data packages (OS Client).
* If deploying redundant single stations, designate Station 1 as Base OS (WinCC Application) and Station 2 as Reference OS (WinCC Appl. (ref)).
Insert Hardware Configurations in SIMATIC Manager:
* Configure the Base PC Station with WinCC Application and communication processor.
* Configure the Reference PC Station with WinCC Appl. (ref) in Slot 1 and matching communication cards.
* Verify that the Station Names match the physical Windows Computer Names of each machine.
Link Reference OS to Base OS:
* Open Object Properties of the Reference OS in SIMATIC Manager.
* Under the Target OS and Standby OS Computer tab, assign the Base OS from the dropdown.
* Configure the target network shared path for the reference station.
Verify Software Licensing on Both Stations:
* Open Automation License Manager (ALM) on the Base PC; verify installed WinCC Runtime PO licenses.
* Open ALM on the Reference PC; verify that an identical WinCC Runtime PO license and WinCC Redundancy license are installed locally.
Compile and Deploy:
* Compile the Base OS project.
* Download Entire OS to the Base PC Station.
* Download Entire OS to the Reference PC Station.

Verification

Launch WinCC Runtime on both stations; verify that both connect to the S7-400 / CPU 410 controllers across the Plant Bus.
Open Automation License Manager on the Reference PC; verify that WinCC Runtime checks out the local license key without 'Demo Mode' warnings.
Disconnect network cables on the Base OS; verify that the Reference OS continues to display real-time process values uninterrupted.

Limitations and Operational Precautions

A Reference OS cannot have customized process graphics or unique tag configurations distinct from the Base OS; any change made to the Base OS will overwrite the Reference OS upon subsequent download. If unique station layouts are required, configure independent WinCC Applications.

Engineer FAQ

Does using a WinCC Appl. (ref) save license costs?

No. Every physical station running a Reference OS requires its own full WinCC Runtime and Process Object licenses. It saves engineering and compilation time, not license costs.