I wrote yesterday about how I located the Oracle alert logs. When I was working (some years ago) with the Oracle 11g database, we had some problems with the Enterprise Manager (EM) and it was necessary to take a peek in the logs.
This information is also valid for 12c. I haven’t checked (or worked with) newer versions than that.
These logs are found in the directory $EMHOME/sysman/log.
If you don’t know, you can get $EMHOME by using the emctl command. For example: