Just run into this interesting post concerning the monitoring of MGMTDB databases as part of Grid Infrastructure, on Neil Chandler’s DBA Blog
However as we know that Oracle 12.1.02 comes with a mandatory Grid Infrastructure Management Repository database (the MGMTDB database) it to my opinion makes sense to monitor it using Oracle Enterprise Manager.
For more information on the GIMR database see the Oracle documentation on it: http://docs.oracle.com/database/121/CWADD/troubleshoot.htm#CWADD92242
What's cooking at Oracle - Rob Zoeteweij 
Did you run into this one as well, Rob? 🙂 http://petewhodidnottweet.com/2015/10/should-i-monitor-the-mgmtdb-database/
Hi Pete, yes I run into this problem as well. However, I do not agree that the MGMTDB should not be discovered. As, you said yourself; it is a database and it needs to be up and running to support the Grid infrastructure…. So, if you ask me; leave the discovery of this database in! It should be up to the user whether or not he wants to monitor it with EM.
Kind regards
Rob
Yes it needs to be up and running, but you can’t connect as DBSNMP therefore it CAN’T be monitored. Hence the reason for leaving it out. You’ll just see false alerts when trying to monitor it. 🙂
Hi Pete, let me check on that. We are actualy montoring it at a customer site and everything monitors nice and easy 😉
You might want to check to update on my post.