Configuring Referenced OS Clients in SIMATIC PCS 7 - Server Data Packages and Network Path Resolution

In SIMATIC PCS 7, a Referenced OS (WinCC Appl. Ref) is a thin client deployment that shares the project data and server package assignment of a master base OS Client. When a Referenced OS displays 'No connection to data server' in runtime, it indicates that the master OS Server providing the runtime process data (tags, archives, and alarms) is offline or that the network share path to the base OS Client project is invalid. To resolve this, ensure the OS Server is in runtime with generated server data packages, configure the target network path in the properties of the Referenced OS, and download the Referenced OS strictly via 'PLC > Download' in SIMATIC Manager rather than manual file copying or Project Duplicator.

Executive Summary

In multi-client SIMATIC PCS 7 control rooms with dozens of identical operator stations, configuring and maintaining individual WinCC OS Client projects creates significant engineering overhead. To streamline deployment, Siemens provides the Referenced OS architecture (WinCC Appl. (Ref)). In this model, multiple physical client workstations execute runtime from a single master base OS Client project template. However, commissioning engineers frequently encounter runtime disconnection alarms where graphic faceplates display 'No connection to data server' and technological blocks (such as MotL and VlvL) show disconnected grayed-out icons. This failure arises from misunderstanding the two-tier data server relationship, improper network share paths, or using invalid project deployment methods (such as Project Duplicator). This technical guide details the configuration and download mechanics for Referenced OS stations.

Referenced OS Architecture: Master OS Client vs Referenced Clients

The Referenced OS concept distinguishes between project engineering templates and runtime execution nodes:

Base OS Client (WinCC Appl.): The master template configured in the SIMATIC Manager multiproject. It holds the graphic pictures (.pdl), scripts, plant hierarchy layout, and assignments to server data packages.
Referenced OS (WinCC Appl. (Ref)): A lightweight PC station object in SIMATIC Manager that points to the Base OS Client. It possesses no independent picture files of its own.

When a Referenced OS client boots into runtime, it reads its pictures from the local folder mirrored from the master template, while establishing real-time tag and alarm communication directly with the central OS Servers.

Why 'No Connection to Data Server' Errors Occur

The error 'No connection to data server' points to one of two distinct communication breakdowns:

OS Server Outage (Data Server Loss): In WinCC client terminology, the 'Data Server' is the physical OS Server (or redundant server pair) that holds the AS communication driver and database. If the OS Server is shut down or rebooting, all OS Clients (both standard and referenced) lose tag updates.
Invalid Target Path in Referenced OS Properties: If the 'Path to the target OS computer' in the Referenced OS properties is misconfigured, the client cannot locate its server data packages (*.pck), preventing it from identifying which server hosts the technological tags.

Server Data Package Assignment and Terminal Bus Resolution

For a Referenced OS to communicate with OS Servers across the Terminal Bus:

The OS Server must compile and execute Generate Server Data to export its packages (<ServerProject>.pck).
The Base OS Client must import and assign these packages (Assign OS Server...).
The Referenced OS inherits these package assignments automatically upon download from SIMATIC Manager.

Standard OS Client vs Referenced OS Architecture Comparison

The following table compares standard WinCC OS Clients against Referenced OS Clients in SIMATIC PCS 7:

| Engineering Feature | Standard OS Client (WinCC Appl.) | Referenced OS Client (WinCC Appl. (Ref)) |
|---|---|---|---|
| Project Storage | Individual WinCC project on ES | Points to master base OS Client template |
| Picture Modifications | Modified individually per client | Changes made to master propagate to all refs |
| Target Computer Path | Configured in OS properties | Configured in Referenced OS object properties |
| Download Mechanism | SIMATIC Manager PLC > Download | SIMATIC Manager PLC > Download (Mandatory) |
| Project Duplicator Use| Supported for standalone WinCC | Strictly Prohibited in PCS 7 Referenced OS |
| Server Data Packages | Assigned manually in client project | Inherited automatically from base client |

Step-by-Step Configuration and Download Procedure

Method 1: Configuring the Base and Referenced OS in SIMATIC Manager

In SIMATIC Manager, create the master OS Client PC Station with application WinCC Appl. (e.g. named OS_Client_Base).
Open OS_Client_Base in WinCC Explorer, configure standard screen resolutions via OS Project Editor, and assign server data packages under Server Data > Assign.
In the multiproject, insert a new PC Station for each physical operator station with application WinCC Appl. (Ref).
Right-click the Referenced OS object, select Object Properties, and navigate to the Target OS and Master OS tab.
Set the Base OS drop-down to OS_Client_Base.
In the field Path to target OS computer, browse or enter the network UNC share path of the physical client computer (e.g. \\CLIENT01\WinCC_Project\).

Method 2: Downloading the Referenced OS Client

Select the Referenced OS object in SIMATIC Manager.
Choose PLC > Download from the top menu bar.
SIMATIC Manager automatically mirrors the base project data, adjusts local station names, and registers the project on the target machine.
On the physical client, launch WinCC Runtime and verify live data updates.

Verification

To verify that the Referenced OS connects to data servers without errors:

Runtime Screen Check: In WinCC Runtime on the Referenced OS, navigate across process pictures. Confirm that valve, motor, and analog block icons display active process values without gray disconnect hatching.
Server State Banner: Confirm that the top alarm line displays no 'No connection to data server' system banners.
Channel Diagnostics: Open the WinCC Channel Diagnosis tool (WinCC_Channel_Diagnosis.exe) on the client. Confirm that the status for all server package connections reads OK (Green).

Limitations and Operational Precautions

Prohibition of Project Duplicator: Never use WinCC Project Duplicator to deploy a Referenced OS. Project Duplicator breaks the internal station binding and converts the project into an orphaned standard client.
OS Server Dependency: A Referenced OS cannot function if the master OS Server is powered down. Redundant OS Server pairs should always be deployed to ensure continuous data server availability.
Simultaneous Downloads: Do not attempt to download multiple Referenced OS clients simultaneously from a single ES; download them sequentially to avoid file locking conflicts.

Engineer FAQ

Can a Referenced OS have unique start pictures different from the base OS client?

No. All Referenced OS clients share identical picture files, start screens, and layout properties defined in the master base client.

Why can't I use Project Duplicator for Referenced OS stations?

Project Duplicator creates standalone copies that do not inherit master template updates, destroying the centralized maintenance architecture.

What happens to Referenced OS clients when the master base client is recompiled?

After compiling the base client, you must perform 'PLC > Download' to each Referenced OS to push the updated graphic pictures and packages.

Technical References

Related Tags

https://industrialautomation.net/search?query=simatic-pcs7
https://industrialautomation.net/search?query=wincc-scada
https://industrialautomation.net/search?query=client-server
https://industrialautomation.net/search?query=operator-station

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Configuring Referenced OS Clients in SIMATIC PCS 7 - Server Data Packages and Network Path Resolution