How to Recover from 'Server Down' on OS Clients After Deleting and Reassigning OS Servers

When a redundant OS Server project folder is deleted and reassigned in SIMATIC PCS 7 (V9.1 SP1), causing OS Clients to display "Server Down" errors, you must execute a complete OS compilation, regenerate the server data package, and download the updated server package to the OS Clients. Deleting an OS project directory destroys the project's unique internal GUIDs and permanently revokes the system's "Online Modification Capability" (delta download). Consequently, client workstations attempt to connect to obsolete database endpoints. To restore client-server communications, recompile the OS Server with entire scope, execute Generate Server Data, re-assign the server package on the OS Client, and download the client projects.

Architecture of WinCC Server Data Packages and Client Assignment

In a distributed SIMATIC PCS 7 OS client-server architecture:
- OS Servers: Host the process communication drivers, tag logging databases, and alarm logging ring buffers.
- Server Data Packages (*.pck): Contain exported descriptors of all available WinCC tags, message categories, graphic picture names, and server network endpoints.
- OS Clients: Do not communicate directly with automation controllers. Instead, an OS Client loads the server's package file. When an operator opens a process picture, the client reads the package to locate the active server over the Terminal Bus.
- Redundancy Management: The package lists both the Master and Standby server network addresses, enabling automatic client failover.

Why Deleting the Project Folder Destroys Online Modification Capability

When an engineer deletes the directory containing the OS Server project and recreates it or changes the target path:
1. Loss of Delta Engineering Context: PCS 7 maintains transactional delta-tracking databases on the Engineering Station (ES) and OS Servers to enable "Changes Only" downloads.
2. The System Warning: SIMATIC Manager displays: After changing the target path or after assigning a standby-OS, the online modification capability is lost. Additionally the OS needs to be newly compiled, and packages for the client are to be updated.
3. Database Re-indexing: A freshly created OS project receives new internal database instance identifiers. The existing server data package on the OS Clients points to the old, deleted database instance, causing clients to report the server as permanently offline or down.

Symptoms of Disconnected OS Clients ('Server Down')

When server data synchronization is broken:
* HMI Banner Alert: The top status banner on OS Clients displays: @Server Down or No connection to data server.
* Graphics Disruption: Process pictures open with yellow warning triangles, exclamation marks, or disconnected gray block icons.
* Alarm List Empty: The incoming alarm list in AlarmControl is completely blank, displaying Disconnected from server.

Method: Step-by-Step Procedure to Restore Redundant Servers and Clients

Follow this strict engineering sequence to resynchronize the servers and restore client visualization:

Step 1: Re-establish OS Redundancy in SIMATIC Manager

In SIMATIC Manager, select the primary OS Server project (e.g., OS_SRV1).
Right-click and open Object Properties:
- Verify that the Target OS path points to the correct network share on physical Server 1.
- On the Redundancy tab, confirm that the partner station is assigned to OS_SRV2.
Open WinCC Explorer on the primary OS Server:
- Open the Redundancy editor in the tree.
- Confirm that the partner computer name, redundant network connection, and archive synchronization options are verified.

Step 2: Perform Full Compilation of the OS Server

Because online modification capability was lost, you must compile the entire scope:
1. In SIMATIC Manager, right-click the primary OS Server and select Compile.
2. In the compile wizard:
- Select Entire Scope for tags and messages.
- Select Entire Scope for SFC visualization and picture tree.
3. Allow compilation to finish with 0 errors.

Step 3: Generate Server Data (Package)

In WinCC Explorer on the primary OS Server, navigate to the Server Data editor in the left navigation pane.
Right-click Server Data and select Generate....
The system generates an updated package file (e.g., OS_SRV1.pck) containing the new database GUIDs and network addresses.
Close WinCC Explorer on the ES.

Step 4: Update Server Data on the OS Client Projects

In SIMATIC Manager, open each OS Client project in WinCC Explorer.
Navigate to Server Data on the OS Client.
Right-click the existing server package and select Update... (or right-click -> Load... and select the freshly generated OS_SRV1.pck).
Right-click the package and select Configure...:
- Set the standard server for Split Screen Manager, Alarms, and User Archives to OS_SRV1.
Close WinCC Explorer on the client projects.

Step 5: Download Projects to Target Stations

In SIMATIC Manager, right-click the primary OS Server and select PLC -> Download:
- Select Entire Scope (Note: requires stopping runtime on Server 1).
Download the standby OS Server (OS_SRV2) with Entire Scope.
Right-click each OS Client and select PLC -> Download (Entire Scope).
Activate WinCC Runtime on Server 1, followed by Server 2, and finally on all OS Clients.

Verification

To verify that the "Server Down" condition is completely resolved:
- On the OS Clients, observe the top system overview strip: verify that the @Server Down banner extinguishes and displays the normal plant hierarchy area buttons.
- Open multiple technological faceplates on the clients: confirm that process values, bar graphs, and motor run states display live dynamic data.
- Open the WinCC AlarmControl table on clients: verify that historical and active alarms populate without error messages.
- In WinCC Explorer on the OS Servers, check the internal system tag @RedundancyState: verify it reads 1 (Server 1 Master) and 2 (Server 2 Standby) with active database replication.

Limitations and Operational Precautions

Mandatory Runtime Shutdown for Full Download: Executing a full download (Entire Scope) requires deactivating WinCC Runtime on the target server. In an operating plant, ensure the redundant partner server is operational and carrying the process load before downloading to the first server.
Terminal Bus Network Checks: If clients still report "Server Down" after package regeneration, verify that the Simatic Shell network adapter binding on the clients and servers points to the dedicated Terminal Bus network card.
Windows Host Name Integrity: Do not rename the OS Server computer in Windows after generating packages without updating the computer name in WinCC Explorer and regenerating packages.

Engineer FAQ

Can I regain 'Changes Only' download capability after this procedure?

Yes. Once the full download (Entire Scope) has been downloaded to the OS Servers and Clients, the delta-tracking engine resets. Subsequent small engineering modifications can be downloaded via "Changes Only" while the plant remains in runtime.

Why did deleting the folder on Server 1 affect the OS Clients?

The clients evaluate package descriptors that reference specific SQL database catalog instances. Recreating the project changes internal GUIDs, causing clients to reject the new server instance until their local packages are refreshed.

How do I generate server packages automatically during compilation?

In SIMATIC Manager, when you compile the OS, the compiler automatically generates updated server packages if the option "Generate server data" is enabled in the compilation wizard settings.

What happens if I download the client while runtime is active?

WinCC OS Clients support online project downloads if only graphics and tags are changed. However, updating core server packages requires closing and restarting WinCC Runtime on the client station.

Technical References

Siemens Industry Online Support: SIMATIC PCS 7 OS Client-Server Configuration Manual.
SIOS Entry 109742323: PCS 7 Compendium Part A - Configuration Guidelines (Section: OS Redundancy and Clients).
SIOS Entry 109809264: SIMATIC Process Control System PCS 7 High Availability Process Control Systems.
Siemens Support Guide: Troubleshooting WinCC Server Data and Redundancy Faults.

Related Tags

WinCC
OS Client
OS Server
Redundancy
Server Down
Server Data
Industrial Automation

How to Recover from 'Server Down' on OS Clients After Deleting and Reassigning OS Servers