I've added a "exception flow" by adding a Exception rule on the Qu

You can use an exception on a Query DB node, but in your scenario it would be best to set the "Pause Node On Error" setting to false, record the error flag into a pv! and use that pv! in a decision node on the regular output path of the DB node. That way the DB node completes with or without error, you can check for an error and flow your process as necessary. We do this currently to force error'd DB nodes to all wait for process to process messaging (before flowing back into itself), so during a DB outage we can resume all processes with one click of a management process instead of hundreds manually one by one.

You can use an exception on a Query DB node, but in your scenario it would be best to set the "Pause Node On Error" setting to false, record the error flag into a pv! and use that pv! in a decision node on the regular output path of the DB node. That way the DB node completes with or without error, you can check for an error and flow your process as necessary. We do this currently to force error'd DB nodes to all wait for process to process messaging (before flowing back into itself), so during a DB outage we can resume all processes with one click of a management process instead of hundreds manually one by one.