We also implemented the alarm for the SNMP uptime datasources, which covers situations where SNMP is misconfigured on not working. It will miss batchscript, script, WMI, etc so it's definitely not comprehensive.
The problem with "No Data", and I've had some back-and-forth with the CSM, is that there is currently no way to tell if the "No Data" is intentional (if the datapoint is not relevant given the current status) or cause for a problem (data should be returned or is not). This shows up in scripts where they will set a datapoint in some paths but not others. The new SNMP interfaces batchscript will return 32 or 64 bit datapoints depending on the interfaces and not return any value for the others, and the new SSL certificate monitor has a lot of datapoints that will only return values in certain situations.
The dev team noted that returning a '0' isn't really correct, but 'No data' is also a problem because it becomes impossible to tell when datasources or devices are not working correctly. I'm pushing on the CSM to prioritize some improvement that can be used to check for problems (clean up the environment) and/or alarm reliably when data isn't being returned.
@mnagel For your instance deletion issue check out this thread; I keep running into this issue and don't think there is a clean way to handle it yet.
/topic/5834-active-discovery-and-instance-deletion/
