In the case where the OPC UA Server subscribes to a value from another OPC UA Server, each Server applies its own serverTimestamp. This is in contrast to the sourceTimestamp in which only the originator of the data is allowed to apply the sourceTimestamp.
If the Server subscribes to the value from another Server every ten seconds and the value changes, then the serverTimestamp is updated each time a new value is received. If the value does not change, then new values will not be received on the Subscription. However, in the absence of errors, the receiving Server applies a new serverTimestamp every ten seconds because not receiving a value means that the value has not changed. Thus, the serverTimestamp reflects the time at which the Server knew the value to be accurate.
- the device is checking values every 0,5 seconds,
- the connection to the device is good,
- the device sent an update 3 minutes ago with a value of 1,234.