Events will not work with Datasets that run as part of the Mirror Service, here's why.
The Event Service helps users better understand their process by allowing for rules to be created and identifing Events based on those rules. However, in order for the service to operate properly, tags that are part of a Mirror Service cannot be used.
When the Mirror operates, it takes time based snapshots of other Historian's DataSets. The new data that has been written since the previous snapshot, is then transfered into the Mirrored DataSet. Events requires a constant scanning of new data, and therefore is not able to handle an absence of updates during the snapshot.
To overcome this, we recommend you "dual log" the data necessary for Events rather than mirror it.