SIMATIC PCS 7 OS Web Server Client Licensing - Accumulation Rules and Cache Refresh in ALM

In SIMATIC PCS 7 V9.0, OS Web Server client access licenses are fully additive in Automation License Manager (ALM). A Web Server possessing a basic server package (e.g. SISLP7WEBS0900) alongside multiple countable client license keys-such as 1x 5 clients (SISCYP7WEB99992) and 1x 10 clients (SIFCYP7WEB99993)-accumulates to authorize a total of 15 concurrent web client sessions. If only 5 clients are admitted initially after transferring a 10-client key, this is caused by WinCC WebNavigator license caching: the active IIS application pool and WinCC Web service do not poll ALM continuously. To immediately activate accumulated client licenses without waiting hours for the background validation timer to expire, execute 'iisreset' from an administrative command prompt on the Web Server.

Executive Summary

Deploying SIMATIC PCS 7 OS Web Servers (WinCC WebNavigator) provides thin-client process visualization across plant local area networks and remote engineering stations without installing thick OS Client software. When expanding web client capacity (e.g. growing from 5 to 15 concurrent users), system administrators purchase and transfer additional countable license keys into Automation License Manager (ALM). A common point of confusion arises when newly transferred licenses appear valid in ALM, but connecting web clients continue to encounter 'Maximum number of clients exceeded' rejections for up to two hours. This article details the manufacturer licensing counting rules for SIMATIC PCS 7 Web Servers, explains the additive accumulation mechanism in ALM, and provides the command to force immediate license cache clearing.

Architecture and Fundamental Mechanics

Web Server Licensing Architecture, Countable Keys, and IIS Runtime Caching:

Architecture of SIMATIC PCS 7 OS Web Server Licenses:
Operating a PCS 7 Web Server requires two distinct license types managed in ALM:
1. Web Server Basic License (e.g. SIMATIC PCS 7 OS Web Server Basic V9.0): Authorizes the server computer to execute the WebNavigator publishing engine and host the Web server portal.
2. Web Client Access Licenses (Count-relevant, e.g. SIMATIC PCS 7 OS Web Server (Count relev.)): Authorize concurrent web client connections, supplied in modular denominations of 1, 5, 10, 25, 50, or 100 clients.
Additive Accumulation Mechanics in ALM:
Unlike major version software engineering bundles, count-relevant Web Client licenses are strictly additive.
If drive C: contains a 10-client license and drive D: contains a 5-client license, ALM aggregates them into a single valid pool of 15 client tokens.
Clients consume one license token dynamically upon logging into the WebNavigator portal via Internet Explorer / WinCCViewerRT, and return the token to the pool upon browser closure.
The Runtime License Caching Bottleneck:
WinCC WebNavigator operates on top of Microsoft Internet Information Services (IIS).
To optimize web server performance and avoid flooding ALM with high-frequency DCOM license queries, the IIS worker process (w3wp.exe) and the WinCC Web service (CCWebPublishing.exe) cache the authorized client count at startup.
When new license keys are moved onto the computer via ALM, the running web application does not immediately detect the updated capacity. The system relies on a slow background polling timer that refreshes license counts every 1 to 2 hours.
Consequently, new web clients are rejected until the internal license cache is flushed via an IIS restart.

Step-by-Step Implementation Procedure

Verify Installed Licenses in Automation License Manager (ALM):
* Open Automation License Manager on the PCS 7 Web Server machine.
* Check all local drives (C:, D:) for active licenses.
* Confirm that the base server license is present: SIMATIC PCS 7 OS Web Server Basic V9.0.
* Confirm that countable client licenses are present and valid (e.g. 1x Count: 5 and 1x Count: 10).
* In ALM, execute View -> Refresh (F5) and select Check License Key to confirm zero licensing faults.
Force Immediate License Refresh via IIS Reset:
* Click the Windows Start menu, type cmd, right-click 'Command Prompt', and select Run as administrator.
* In the command window, execute the standard IIS service restart command:
iisreset
* Windows terminates the IIS worker process and cleanly restarts World Wide Web Publishing services:
- Attempting stop... Internet services successfully stopped.
- Attempting start... Internet services successfully restarted.
Restart the WinCC Web Service (If Necessary):
* If clients are still blocked, open the Windows Services console (services.msc).
* Locate SIMATIC WinCC WebNavigator Server (or CCWebPublishing).
* Right-click and select Restart.
Verify Client Capacity in WebNavigator Administration Tool:
* Open the Web Configurator or WebNavigator Administrator tool from the Siemens Start menu folder.
* Check the server status summary: Confirm that 'Max. Number of Clients' now displays 15.
Validate Concurrent Client Logins:
* From client workstations, launch WinCCViewerRT.exe or browse to the web server URL.
* Connect multiple sessions concurrently (e.g. 6 to 15 clients).
* In ALM, verify that the 'In use' column for the countable client licenses dynamically increments to match active sessions.

Verification

Verify License Accumulation and Multi-Client Access:
1. In ALM, verify that the total available license count across all OS Web Server keys equals 15.
2. Connect 10 or more web clients simultaneously; confirm that no client encounters license rejection popups.
3. In the Windows Event Viewer under Application Logs, verify that zero license deficit warnings for WinCC WebNavigator are generated.

Limitations and Operational Precautions

Operational Precautions and Commercial Guardrails:
- Running iisreset momentarily disconnects active web client sessions (typically for 5 to 10 seconds); execute the command during shift transitions or notify operators beforehand.
- Commercial Rule: Web client licenses do not authorize thick OS Clients; thick OS Clients require dedicated SIMATIC PCS 7 OS Client runtime packages.
- Always validate final license quantities and exact MLFB order numbers against the applicable Siemens catalog and authorized distributor quotation.

Engineer FAQ

Do SIMATIC PCS 7 Web Server client licenses accumulate additively?

Yes. Countable Web Server client licenses are strictly additive in ALM. A 5-client key and a 10-client key combine to authorize 15 concurrent web client sessions.

Why did it take 2 hours for my new 10-client license to work?

WinCC WebNavigator caches license counts in Microsoft IIS to optimize web performance. It polls ALM on a slow background cycle (1-2 hours) unless forced to refresh.

How do I immediately activate newly added Web Server licenses?

Open an administrative Command Prompt on the Web Server and run iisreset to immediately flush the license cache.

What is the difference between Web Server Basic and Web Server Count licenses?

Web Server Basic licenses the server computer to host the WebNavigator service, while Count relev. licenses authorize the specific number of concurrent client browser sessions.