Professional OPC
Development Tools

logos

Online Forums

Technical support is provided through Support Forums below. Anybody can view them; you need to Register/Login to our site (see links in upper right corner) in order to Post questions. You do not have to be a licensed user of our product.

Please read Rules for forum posts before reporting your issue or asking a question. OPC Labs team is actively monitoring the forums, and replies as soon as possible. Various technical information can also be found in our Knowledge Base. For your convenience, we have also assembled a Frequently Asked Questions page.

Do not use the Contact page for technical issues.

XML-DA. Change subscribe parameters

More
21 May 2020 07:35 #8495 by Andriy
Hello,
Sorry for the delayed response. You are right, I'm troubleshooting the case when server takes long time to respond with basic polling approach.
Actually, I'm awaiting feedback from Siemens OPC support. I will let you know if that advanced configuration is still relevant

Best regards

Please Log in or Create an account to join the conversation.

More
16 May 2020 09:01 #8488 by support
Thank you for explanation. I understand - it makes sense. The fact is, the approach used was largely OK with advanced polling, but is not ideal when basic polling is used plus the server takes long to respond, which is your case.

For design reasons we cannot put the additional into objects like DAGroupParameters which are given to every subscription. If we are going to implement it, it would be something like an additional factor (multiplier) in the structure of EasyDAClient parameters - e.g. you would be able to say "call SubscriptionPolledRefresh 2.5 times slower than the update rate (the requested sampling rate)".

This can be done, but only to a new version (API change). Unfortunately, we have scheduled a longer "pause" in version releases; do not expect a new version sooner than in September, probably. Let me know what your position on this is.

Best regards
The following user(s) said Thank You: Andriy

Please Log in or Create an account to join the conversation.

More
13 May 2020 10:17 #8483 by Andriy
Hello,

Thank you for your information.
I'm using Basic poll refresh approach.
I need to specify 2 sec for RequestedSamplingRate but call SubscriptionPolledRefresh each 5 sec.
It would be nice to have possibility to specify SubscriptionPingRate also. That is, set SubscriptionPingRate being 2 times longer than the update rate.

Best regards

Please Log in or Create an account to join the conversation.

More
13 May 2020 08:58 - 13 May 2020 08:58 #8482 by support
Hello,

I do not write understand your question, because it postulates an assumption that is not true. The Subscription PolledRefresh is normally called at a rate different from a value of SubscriptionPingRate.

The computations are more complicated and there are conditions under which the behavior will be different, but normally, the SubscriptionPingRate end up being 10 times longer than the update rate you specify for the items in the subscription.

With basic polled refresh, the rate at which QuickOPC will then call SubscriptionPolledRefresh will also be the update rate of the items in the subscription.,

With advanced polled refresh then, the actual rate at which QuickOPC will call SubscriptionPolledRefresh depends on the responses of the server. The time between subsequent SubscriptionPolledRefresh may fluctuate between update rate of the subscription (if there are changes immediately available) and the SubscriptionPingRate (in case there are no changes in values). In this case, if there are no changes in values for extended period of time, it can truly happen that the rate of SubscriptionPolledRefresh calls will be roughly the same as SubscriptionPingRate.

To me this is all the way it is supposed to work, and I do not see an issue with it. I need to know what is the actual problem you are trying to solve.DO not forget to tell whether you are using Basic or Advanced poll refresh.

Best regards
Last edit: 13 May 2020 08:58 by support.

Please Log in or Create an account to join the conversation.

More
08 May 2020 16:52 #8475 by Andriy
Hello,

Is it possible to set "RequestedSamplingRate" , "SubscriptionPingRate" attributes of a Subscribe request and call SubscriptionPolledRefresh at a rate different from a value of "SubscriptionPingRate"?
e.g RequestedSamplingRate = 2000 ; SubscriptionPingRate = 10000; call SubscriptionPolledRefresh each 5 sec

Regards

Please Log in or Create an account to join the conversation.

Moderators: support
Time to create page: 0.048 seconds