Normally, when the host health is not healthy, I can hover my mouse over to the exclamation mark and it would tell me the reason (something like "for the past 15 minutes, there is violation of....").
In this case, the IIS process only tells me it isn't healthy, and nothing more than that, and based on what I see in the 4 graphs, I can't any clue.
Anyone has any idea why it raise unhealthy warning?
Your process metrics are not showing after around 6pm on the 19th (threads, transfer rate, requests), but your host metrics continue (CPU). That is most likely why you are getting the unhealthy message. Can you confirm your IIS process is still running?
Yes, IIS is still running, only this ....AppPool somehow seems to be shutdown 'ungracefully', and then another new one (with different PID and of course, only has data starting from 6pm 19th Sept) has been spawned.
But, the process should then be offline (grey) instead of unhealthy (red) isn't it?
Was there another process spun up when the old one died, potentially with an index at the end of the name (for example ISS_process) in the Dynatrace host infrastructure dashlet? Maybe your metrics are there since your process died in a not graceful way. If that is the case then I would ignore the process unhealthy message from the one that is pictured in the screenshot as it should disappear entirely in a few days.