SIMATIC WinCC Open Architecture Forum

Hello All,

I want to learn more about number of OPC UA Client subscription that WinCC OA Can handle concurrently. We need around 1500 concurrent subscriptions to listen sensor data, so is it possible?

In 3.19 documentation for OPC UA Subscription below mentioned

The WinCC OA OPC UA client is able to sign up for value changes, events and alarms to an OPC UA server for autonomous notifications within one or several subscriptions. The number of subscriptions is not limited.

When I ask chat gpt (it can be a total made up information but I want to share anyways), I get this answer for wincc oa 3.19

The maximum number of OPC UA subscriptions has been increased to 2000 for the OPC UA Client Manager. The maximum number of monitored items per subscription is 1000

Does anyone know the real information about it?

Thanks

The number of subscriptions is less important than the value changes per second. Even with a single subscription, you can already cause the data and event manager to be overloaded.

I have asked the chat bot the following question: What are the limits for the subscriptions for OPC UA?

The following answer was received:
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The limits for OPC UA subscriptions in WinCC OA are as follows:

-- Number of Subscriptions: There is no limit on the number of subscriptions that can be created. However, each subscription can only be assigned to one server.
-- Monitored Items: The maximum monitored item buffer size of the WinCC OA Server is 100 by default. This can be configured via the uaMaxDataQueueSize configuration entry.
-- Buffered Data: It is recommended not to exceed a total number of buffered data of 1,000,000 to avoid heavy load on CPU and memory.
-- Session Timeout: The session timeout should be less than 20,000 seconds.
-- Queue Size: The queue size should be less than 10,000.
-- Connections per Driver: The recommended/technical limit of connections per OPC UA driver is 50.

These limits are recommended to ensure optimal performance and to avoid overloading the system.
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As already mentioned you must have a look at the overall system performance and the CPU/memory load to detect if the system is capable of processing the load.

Best Regards
Leopold Knipp
Senior Support Specialist

Why do you need that much subscriptions? Multiple values can be read with a single subscription.