Slow OPC client update with IGSS OPC server

FAQ Question

I’m using OPC clients connected to the IGSS OPC server and I see that the clients don’t seem to be updating very quickly. What can I do to improve performance?


To achieve the shortest update delay, you must carefully consider how you group the OPC Items being used. The shortest delay occurs when only a few groups are defined and the longest when there are many, and this is especially true if every Item has its own group. In some cases this results in an extremely sluggish system operating way below the norm. Here is some advice:

Make one group solely for digital objects. In this group you would place all OPC Items which require a really rapid update. Here the Update Rate and Dead Band are set to 0.

Make other groups for analog objects. In these groups, you would place the OPC Items that will go on functioning despite loss of a few update cycles. These groups would then be set to have a longer update interval in Update Rate. The OPC client thus reserves CPU power for the items whose Update Rate has been set to 0. Apart from the group reserved for digital objects, the OPC client should not request updates faster than the SCADA system is able to deliver them, otherwise nothing is accomplished but a waste of valuable CPU power.