A single-user WinCC station runs engineering and runtime on one PC. A multi-user system has one server with several clients that load their data through packages. A distributed system has several servers, each owning part of the plant, with clients pulling packages from all of them. Redundancy pairs two servers that synchronise archives after a failure.
- Pick the architecture from the number of operator stations and the plant split, not from the tag count alone.
- Packages are how a client learns what a server owns; a stale package is the usual cause of missing tags on a client.
- Redundancy protects availability, not data quality; both servers still depend on the same PLC connection.
Single-User, Multi-User and Distributed Systems
WinCC scales through three configurations, and choosing correctly at the start avoids an expensive migration later.
| Configuration | What it is | Typical use |
|---|---|---|
| Single-user system | One PC running configuration and runtime, connected directly to the PLCs | One machine or a small line with a single operator station |
| Multi-user system | One server holding the project and archives, with clients displaying it | A plant area with two to several operator stations |
| Distributed system | Several servers, each responsible for part of the plant, with clients accessing all of them | Large plants split by area or process unit |
| Web client | Browser access to a WinCC server through the Web Navigator option | Read-only supervision, remote or management access |
The deciding factor is usually how many people need a screen at once and whether the plant divides naturally into areas. Tag count matters for licensing and performance, but a 20,000-tag plant with one control room is still a multi-user system, not a distributed one.
Plan the split by process unit, not by building. A server that owns half of one unit forces every client to talk to two servers for a single screen.
Servers, Clients and Packages
In a multi-user or distributed system, the server holds the project, runs the channels to the PLCs, and maintains the archives. A client has no PLC connection of its own; it displays data the server provides.
The mechanism that connects them is the package. A server generates a package describing its tags, messages, archives and screens, and each client loads it.
- Configure the server project with its tags, alarms and archives.
- Generate the server data package in the server project.
- Load the package into each client project.
- Regenerate and reload the package whenever the server configuration changes.
Step four is the one that gets skipped. A tag added on the server but not carried into a regenerated package simply does not exist for the client, which shows as a missing value or a broken dynamic on an otherwise healthy screen.
Clients can be configured with their own start screen, language and user rights, so an operator client, an engineering client and a supervisor client can all use the same server with different views. The tag structure behind all of this is covered in WinCC tag types for S7-1500.
Redundancy and Archive Synchronisation
Redundancy pairs two identically configured servers. One runs as master, the other as standby, and each monitors the other over a dedicated connection.
- Failover: if the master fails, clients switch to the standby automatically and operation continues.
- Archive synchronisation: when the failed server returns, the gap in its message and process value archives is filled from its partner.
- Tag synchronisation: internal tags marked for synchronisation are kept aligned between the two servers.
- User archive synchronisation: recipe and parameter records are also brought back into step.
Redundancy protects against a server failure. It does not protect against a network switch failure on the PLC side, a bad configuration downloaded to both servers, or a PLC fault. Design the network path separately: separate switches, separate power supplies, and a dedicated redundancy link between the two servers.
| Requirement | Architecture answer |
|---|---|
| Operation must continue if a PC fails | Redundant server pair |
| Several operators need the same view | Multi-user system with clients |
| Plant divides into independent units | Distributed system, one server per unit |
| Management wants read-only visibility | Web client |
| Archive data must survive for years | Archive backup to a network share or historian |
Plan and build a real WinCC architecture
SCADA sessions cover server and client setup, packages, redundancy and archive design on live projects.
Network, Channels and Screen Hierarchy
The architecture on paper still has to move data. Three things decide whether it performs.
Channels and connections
Each PLC connection uses a communication driver, most often the SIMATIC S7 Protocol Suite for S7-300, S7-400 and S7-1500, or OPC UA for third-party controllers. Group tags that update together into structured tags so the driver reads them in fewer, larger requests instead of many small ones.
Update cycles
A tag read every 500 ms when it changes twice a shift is wasted bandwidth. Set the acquisition cycle per tag according to how fast the value actually moves, and use the picture cycle so a tag is read only while the screen showing it is open.
Screen hierarchy
Mirror the architecture in the screens: a plant overview at the top, one area overview per server or unit below it, then detail screens and faceplates. Operators should reach any detail screen in two clicks from the overview.
Keep the navigation permanent on a screen template so it behaves identically on every client. Sequence and status screens sit at the area level; see the WinCC sequence overview screen.
Hands-On Lab: Configure a WinCC Server and Client
Hands-on- Two WinCC installations, or one PC with a client project for simulation
- A server project with tags, one message and one archive
- Network access between the two stations
- Estimated time: 45 minutes
Prepare the server project
Confirm the server project has tags, an alarm and a process value archive configured.
Generate the package
Generate the server data package from the server project.
Create the client project
Create a client project and load the server package into it.
Build a client screen
Add a screen on the client displaying a server tag and an alarm control.
Test a configuration change
Add a new tag on the server, then check the client before and after regenerating and reloading the package.
The client shows server data without its own PLC connection, and you can demonstrate that a package regeneration is required after every server configuration change.
Frequently asked questions
What is a package in WinCC?
A package is the configuration data a server exports so clients know its tags, messages, archives and screens. Clients load the package; without an up-to-date one they cannot see new server configuration.
When do I need a distributed system instead of multi-user?
When the plant divides into units that are best owned by separate servers, or when one server cannot carry the tag, archive and client load. A single control room with several stations is normally multi-user.
Does redundancy protect against a PLC failure?
No. Redundancy covers a WinCC server failure and synchronises archives afterwards. PLC, network and power failures need their own design measures.
Can a WinCC client connect to more than one server?
Yes, in a distributed system a client loads packages from several servers and can display data from all of them on the same screen.