Executing Online Project Downloads to Redundant WinCC OS Servers Without Plant Interruption

In SIMATIC PCS 7 V8.2, downloading project modifications (such as new analog tags and PID loops) to a redundant WinCC OS server pair without plant disruption requires following the strict redundant OS download procedure. Never execute a full download or download to the Master server while it is actively serving clients. Instead, generate and verify the server data package on the Engineering Station, execute 'Changes only' download to the Standby OS server first, confirm runtime activation and database synchronization via @RedundancyState on the Standby server, switch client connections to the Standby server, and finally download 'Changes only' to the Partner server. For redundant OS systems, verify that runtime licenses are installed on each physical server with an authorized Siemens distributor or the Siemens Industry Mall.

Executive Summary

Plant modifications—such as commissioning a new analog transmitter or fine-tuning a PID controller—require propagating new tags, alarms, and graphic symbols from the Engineering Station (ES) to the operational Human-Machine Interface (HMI). In a continuous processing plant running redundant PCS 7 V8.2 WinCC OS servers, an improper download sequence can disconnect operator clients, cause archive data loss, or trigger server redundancy failure. This guide provides the step-by-step, non-disruptive engineering workflow for compiling and downloading OS changes to redundant servers while maintaining 100% plant visibility.

Architecture and Fundamental Mechanics

The PCS 7 redundant OS server architecture provides fault tolerance and bump-free switchover through precise synchronization mechanisms:
1. Master/Standby Server Roles:
- One physical server acts as 'Master' (e.g., OS_SRV1) communicating actively with AS controllers, processing alarms, and serving operator clients.
- The second physical server acts as 'Standby' (e.g., OS_SRV2), continuously mirroring archives and process tags across the redundant serial/Ethernet redundancy link.
2. Delta OS Compilation and Server Data Packages:
- When new CFC blocks (e.g., PIDConL, Pcs7AnIn) are added, an OS Compilation (Scope: Changes) creates new WinCC tags, message definitions, and archives on the ES.
- Compiling generates the updated Server Data package (<ProjectName>.pck), which contains the communication routing information for operator clients.
3. The Asymmetric Download Sequence:
- WinCC allows online delta downloading ('Changes only') directly into active runtime.
- However, downloading to a server causes a momentary reload of graphic pictures, tag management, and script engines.
- To ensure zero operator disruption, the download must always be executed on the Standby server first. Once the Standby server reloads and synchronizes, it is promoted to active, allowing the former Master server to be updated in isolation.

Step-by-Step Implementation Procedure

Perform and Verify OS Compilation on the Engineering Station:
a. Open SIMATIC Manager on the ES.
b. Right-click the OS Server object (e.g., OS_SRV1) and select Compile.
c. In the OS Compilation wizard, select the associated AS controllers.
d. Under 'Scope', select Changes.
e. Complete compilation and verify 0 Errors in the compiler log.
Identify Active Master vs Standby Server:
a. On the operator clients or OS servers, inspect the @RedundancyState internal system tag or open WinCC Redundancy Status.
b. Confirm which server is currently in state Master and which is in state Standby (assume OS_SRV1 is Master and OS_SRV2 is Standby).
Download Changes to the Standby Server (OS_SRV2):
a. In SIMATIC Manager on the ES, right-click the Standby server object (OS_SRV2) and select PLC -> Download.
b. In the download dialog, verify the target path matches the network share of OS_SRV2.
c. Under 'Scope', select Changes.
d. Click 'OK' to initiate download. WinCC transfers modified project files and reloads runtime tables without halting the active Master.
Verify Standby Server Synchronization:
a. On OS_SRV2, open the WinCC diagnostic window (apdiag.exe or WinCC status bar).
b. Verify that @RedundancyState indicates successful reload and that archive synchronization begins.
c. Wait until the redundancy status indicates 'Redundant' and archive synchronization is complete.
Switch Client Operations and Download to the Partner Server (OS_SRV1):
a. Deactivate runtime on OS_SRV1 or use the redundancy failover control to make OS_SRV2 the active server.
b. Verify that all OS Clients seamlessly switch to OS_SRV2 without losing faceplates or trends.
c. On the ES, right-click OS_SRV1 in SIMATIC Manager and select PLC -> Download.
d. Select Changes and execute the download.
e. When download completes, activate runtime on OS_SRV1 and allow redundancy synchronization to complete.

Verification

In WinCC Explorer on both OS servers, check internal tag @RedundancyState: verify one server reports Master (value 1) and the other reports Standby/Redundant (value 2).
On an OS Client, open the newly created PID faceplate: verify live setpoint, process variable, and manual output control.
Trigger an alarm on the new channel: confirm the alarm appears simultaneously on both OS servers and on all OS clients.

Limitations and Operational Precautions

If changes include modifications to the WinCC Computer Name, Redundancy configuration, or major database schema changes, 'Changes only' download is blocked, requiring a planned, sequential server shutdown.

Engineer FAQ

Which server should be downloaded first in a redundant OS pair?

Always download the Standby server first. This ensures operator clients remain actively serviced by the Master server during the update.

What happens to operator clients during a 'Changes only' download?

Clients continue running without interruption because they remain connected to the active Master server while the Standby server is updated.

How do I verify that redundant OS servers are fully synchronized?

Check the internal system tag @RedundancyState in WinCC. Both servers should indicate active redundancy without pending sync flags.

Can I perform an OS download if WinCC Runtime is deactivated on the ES?

Yes, OS downloads originate from the Engineering Station to the remote servers; ES runtime does not need to be active.

Are separate runtime licenses required for each redundant WinCC server?

Yes. Each physical OS server in a redundant pair requires an independent WinCC OS Runtime license and Redundancy license.

Technical References

Related Tags

Redundant OS
WinCC Download
Changes Only
PCS 7 V8.2
@RedundancyState
Zero Downtime

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Executing Online Project Downloads to Redundant WinCC OS Servers Without Plant Interruption