Jouni Aro said
The Delphi name for this type is varUInt64. By default, I would expect all variant values to be supported in the communication, but depends also on how you are using it in the application level. Are you maybe trying to connect it to a TPsInteger with TPsOPCConnector? That one only holds 32-bit integers. Please, try TPsVariant instead.  

I use the next way.

TPsVariant *vv = new TPsVariant (0);
vv->Caption = name;
vv->OnChange = onDataChanged;
TPsVarLink *v = connector_->AddItem (name, vv, vpValue);

But I get into onDataChanged method only few times.

Jouni Aro said
Well, are you sure that it should change more often? Have you checked with other clients, for example Prosys OPC Client to see what changes the server is actually sending?

You can also enable the Log in TPsOPCServer to see all communication that is happening between the server and your application.  

It works with other clients. The problem exactly with this field type because if I select all field except this one I get updates but with this field selected I don’t have updates for all fields.
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The log file:

2020/09/02 22:33:14.628 Connected to Server ‘{7BC0CC8E-482C-47CA-ABDC-0FE7F9C6E729}’ {7BC0CC8E-482C-47CA-ABDC-0FE7F9C6E729}
2020/09/02 22:33:14.650 IConnectionPointContainer.FindConnectionPoint: Result=0x0 (OK)
2020/09/02 22:33:14.665 IConnectionPoint.Advise: Result=0x0 (OK)
2020/09/02 22:33:14.678 IOPCServer.GetStatus: Result=0x0 (OK)
2020/09/02 22:33:14.690 Status changed from ‘No connection!’ to ‘Running’
2020/09/02 22:33:14.704 IOPCServer.AddGroup: Result=0x0 (OK)
2020/09/02 22:33:14.718 IConnectionPointContainer.FindConnectionPoint: Result=0x0 (OK)
2020/09/02 22:33:14.731 IConnectionPoint.Advise: Result=0x0 (OK)
2020/09/02 22:33:14.743 IOPCServer.AddGroup: Result=0x0 (OK)
2020/09/02 22:33:14.757 IOPCItemMgt.AddItems: Result=0x0 (OK)
2020/09/02 22:33:14.772 IConnectionPointContainer.FindConnectionPoint: Result=0x0 (OK)
2020/09/02 22:33:14.785 IConnectionPoint.Advise: Result=0x0 (OK)
2020/09/02 22:33:14.799 Invalid transaction
2020/09/02 22:33:16.836 Invalid transaction