Any adverse impact on
application if the AppMon server is switched off!
Meaning would the
application ( Java, .Net, WebServer ) or any kind would continue to function
with no errors if the host on which AppMon is running is down.
Would there be any impact
on client side log directory filling up etc?
There should be no issue, in general agents will not be able to send data. If switch off is temporary, agent and collectors has some cache, so they will not have any impact. If you want permanently shut down server, they will work as usual but data will be lost.
But I suggest checking application start as well, we had issues with WAS as well for appmon and Dynatrace, when agent wasn't able to connect to anything, process sometimes wasn't able to start
I agree with Sebastian. If you want to shut down the AppMon server permanently the best practice would be to remove the agents or least stop them so that they are not trying to connect to a non-existent server.