Hello,

What exactly do you mean by “update rate”? Subscriptions have Publishing Interval and MonitoredItems have Sampling Interval and when I set both of these to 5 seconds I get PublishResponses containing DataChangeNotifications every 5 seconds as expected.

However, if you do set the Publishing Interval to 1 second and Sampling Interval to 5 seconds, then you will get a new value every second instead of every 5 seconds. This is a known issue so we recommend avoiding using Publishing Intervals that are shorter than Sampling Intervals of MonitoredItems in the Subscription.

Hello,

Simulation Interval and Publishing Interval have no relation with each other. Publishing Interval is a parameter of a Subscription requested by a Client and Simulation Interval is just an internal parameter of Simulation Server.

When Publishing Interval is shorter than Sampling Interval, there shouldn’t be new data changes for every Publishing Interval cycle and sending a Publish Response would be skipped for those cycles. For example, if your Publishing Interval is 1 seconds and Sampling interval is 5 seconds, it would be expected that the first Publish Response would contain the initial values of the MonitoredItems, then there would be four cycles without Publish responses and then on the 5th cycle a Publish Response would be sent again. Publish Responses following that on would be sent on the 10th, 15th, 20th cycles and so on.

If the difference between the Publishing Interval and Sampling Interval is very large, a keep alive message will be sent based on maxKeepAliveCount Subscription parameter to let the Client know that the Subscription is still alive, but there have been no data changes to report. For example if Publishing Interval is still 1 second, maxKeepAliveCount is 5 and Sampling Interval is 10 seconds, then on the 5th cycle a keep alive message would be sent, on the 10th cycle new data changes would be sent, on the 15th cycle another keep alive would be sent and so on.

If you’re interested in learning more about MonitoredItems and Subscriptions, please take a look at https://reference.opcfoundation.org/Core/Part4/v104/docs/5.12.1 and https://reference.opcfoundation.org/Core/Part4/v104/docs/5.13.1

What is happening in Simulation Server is that the MonitoredItems are forced to sample more often than their Sampling Intervals would suggest, which is why there are new data changes to report for each Publishing Interval cycle. This is a known limitation and at the moment you should use Publishing Intervals that are equal to or longer than Sampling Intervals of MonitoredItems in the Subscription to get the expected results.