You can configure each group in the OPC Client to read data from the OPC server’s internal cache or from an actual device. Reading from the cache returns the last value read by the OPC server. The server updates the cache based on the group’s update rate.
Reading from an actual device returns the latest values from the process hardware. Although the latest value is obtained, reading from a device can cause undue stress on the system. For this reason, we recommend that you only use device reads for diagnostic and troubleshooting purposes.
