Analyzing Data Synchronization Mechanics and Ordering Licenses for PCS 7 OS Redundancy

In SIMATIC PCS 7 OS Redundancy, 'Data Synchronization' refers strictly to the automatic equalization of historical runtime databases between redundant partners following a network interruption or server restart: the active WinCC Redundancy agent synchronizes Alarm Logging archives, Tag Logging slow/fast process values, and User Archives. It does not synchronize offline engineering files. To license a redundant system in PCS 7 V9.0: 1. For Single Station Redundancy, order package 6ES7652-3AA58-2YA0 (PO 100); 2. For Server Redundancy, order package 6ES7652-3BA58-2YA0 (PO 100); and 3. For redundant S7-400H communication via CP 1623 (6GK1162-3AA00), order SIMATIC NET S7-REDCONNECT (6GK1716-0HB14-0AC0). Clients can only connect to OS Server Redundancy, never to Single Stations.

Executive Summary

High availability in process automation depends on robust Human-Machine Interface (HMI) redundancy to guarantee continuous process visibility and uninterrupted regulatory archiving. Control engineers configuring redundant operator stations in SIMATIC PCS 7 V9.0 frequently seek clarity on the exact operational meaning of 'Data Synchronization'—specifically whether setpoint adjustments, operational commands, or engineering files sync across stations—and require validation of the exact Siemens catalog order numbers (MLFBs) for hardware and software licensing. This article provides an authoritative breakdown of WinCC Redundancy database equalization mechanics, analyzes client connectivity constraints, and details the verified licensing package schedule for Single Station versus Server architectures.

Architecture and Fundamental Mechanics

WinCC Redundancy Engine, SQL Synchronization Mechanics, and Licensing Framework:

What 'Data Synchronization' Actually Means in WinCC Redundancy:
Independent Data Acquisition: In normal runtime operation, both redundant partner stations (Master and Standby) communicate independently with the automation controllers (AS) over the Plant Bus. Both servers independently read process values, evaluate alarms, and write records to their local Microsoft SQL Server databases.
The Failure Scenario: If OS Server A fails, is taken offline for maintenance, or loses network connection, OS Server B continues acquiring data and logging alarms independently. Server B records an internal downtime marker indicating when Server A stopped responding.
The Synchronization Process: When Server A powers back on and restarts WinCC Runtime, the WinCC Redundancy Synchronization Agent (CCRedCom.exe) engages:
1. It queries Server B to determine the exact time window of Server A's outage.
2. It extracts all missing records from Server B's local SQL database: Alarm Logging (messages, acknowledgments), Tag Logging Fast/Slow (historical process values), and User Archives.
3. It streams and merges these records across the redundancy link into Server A's SQL database.
4. Once complete, both servers possess identical, gap-free historical records.
What Synchronization Does NOT Do: Redundancy does NOT synchronize uncommitted operator screen inputs, internal non-retentive tags, or offline engineering files. Both stations already execute identical project logic compiled from the central ES.
Architectural Differences: Single Station vs Server Redundancy:
OS Single Station Redundancy: Two standalone PCs that act as combined server/client operator interfaces. CRITICAL RULE: OS Clients CANNOT connect to an OS Single Station redundant pair.
OS Server Redundancy: Dedicated background data servers serving up to 64 independent OS Client operator terminals.
Software Licensing Analysis and MLFB Breakdown:
Single Station Redundancy Package (6ES7652-3AA58-2YA0):
- Includes licenses for two Single Stations, WinCC Redundancy, and 100 Process Objects.
Server Redundancy Package (6ES7652-3BA58-2YA0):
- Includes licenses for two OS Servers, WinCC Server, WinCC Redundancy, and 100 Process Objects.
CP 1623 & S7-REDCONNECT:
- Hardware CP 1623 (6GK1162-3AA00): PCI Express communication processor.
- S7-REDCONNECT Powerpack / License (6GK1716-0HB14-0AC0): Mandatory software to manage redundant S7 connections to S7-400H CPUs.

Step-by-Step Implementation Procedure

Select the Proper Architecture Based on Client Needs:
* If the plant requires only two operator consoles: select OS Single Station Redundancy.
* If the plant requires remote clients or more than two consoles: select OS Server Redundancy.
Procure the Validated License Packages (PCS 7 V9.0):
* Option A: For Redundant OS Single Stations (2 PCs):
- 1x 6ES7652-3AA58-2YA0: SIMATIC PCS 7 OS Single Station Redundancy V9.0 (PO 100).
- 2x 6GK1162-3AA00: SIMATIC NET CP 1623 PCI Express Card.
- 2x 6GK1716-0HB14-0AC0: SIMATIC NET S7-REDCONNECT Powerpack (if connecting to S7-400H).
- Option B: For Redundant OS Servers + Clients:
- 1x 6ES7652-3BA58-2YA0: SIMATIC PCS 7 OS Software Server Redundancy V9.0 (PO 100).
- Nx 6ES7652-0XX58-0YB5: SIMATIC PCS 7 OS Software Client V9.0 (1 license per client PC).
- 2x 6GK1162-3AA00: CP 1623 for OS Server 1 and Server 2.
- 2x 6GK1716-0HB14-0AC0: S7-REDCONNECT for OS Server 1 and Server 2.
Configure Redundancy in WinCC Explorer:
* Open the WinCC project on Server 1.
* Double-click Redundancy in the project navigation tree.
* Check Activate Redundancy.
* Define the 'Redundant Partner Server' computer name.
* Check 'Connection to redundant partner via network card' and select the dedicated redundancy adapter.
* Check 'Synchronization of all archives after failure' (Alarm Logging, Tag Logging, User Archives).
* Save and deploy to both servers.
Verify License Transfer in Automation License Manager:
* Transfer server redundancy keys to both stations.
* Verify that ALM shows no missing license warnings.

Verification

Launch WinCC Runtime on both redundant partners.
Verify in WinCC Explorer that the internal tag @RedundancyState reads 1 (Master) on Server 1 and 2 (Standby) on Server 2.
Disconnect the network cable of Server 2 for 10 minutes, generating test process alarms and trend data.
Reconnect Server 2; observe @RedundancyState change to 3 (Synchronizing).
After synchronization completes (@RedundancyState returns to 2), open the Alarm Logging control on Server 2; confirm all alarms generated during the 10-minute outage appear seamlessly.

Limitations and Operational Precautions

WinCC Redundancy synchronization requires high-bandwidth, low-latency connectivity; never route redundancy synchronization across routed corporate WANs or high-latency wireless links. Single Station Redundancy cannot be converted to Server Redundancy without modifying SIMATIC Manager station types and exchanging software licenses. Validate all MLFBs with an authorized Siemens distributor.

Engineer FAQ

What does 'Data Synchronization' mean in PCS 7 OS Redundancy?

It means equalizing the historical SQL databases (Alarm Logging messages and Tag Logging archive values) after a server outage so both stations have identical historical records.

Can clients connect to an OS Single Station redundant pair?

No. OS Clients can only connect to dedicated OS Servers. Single Stations do not support client connections.

Does one redundancy license package cover both computers?

Yes, both the Single Station Redundancy and Server Redundancy packages (6ES7652-3AA... / 6ES7652-3BA...) provide licenses for both computers in the pair.

What license is required to communicate with S7-400H via CP 1623?

SIMATIC NET S7-REDCONNECT (6GK1716-0HB...) is required on each OS server communicating with a redundant S7-400H CPU over Industrial Ethernet.

How do I expand Process Object capacity beyond 100 PO?

Order additive count-relevant PO packages (SIMATIC PCS 7 OS Software Server / Single Station (Count relev.)) in increments of 100, 1000, or more POs.