I would like to re-open the the original question raised by Colin because I am also facing the same problem in most of my PI OPC interfaces.
I had to stop/Start the interface after creatting the tag in order to make it read data.
The behaviuos is always not same
1. Some times tag will read immediatly.
2. Some times it will take ages to start reading
3. Some times it never read until I restart the intraface
I am connecting to variety of OPC servers. Matrikon, Deltav, Yokogawa, Foxboro & Honeywell. I am facing this issue on all type of OPC servers.
What might be the bottleneck to cuase this problem?