EM12c: setting an alert for Recovery Area full conditions

We are currently using EM 12cR4 to monitor our databases.

We just had an incident where a database recovery point had been created and then was forgotten. Eventually, the recovery area filled up and the database stalled. EM sent out an alert when the area was at 99.6 percent full, too late to do anything about it. To prevent this issue from happening, I am trying to set an earlier threshold for this metric. For some odd reason, this metric does not show up in the metric templates for databases and when I view the 'all metrics' display for a database, it does not provide the option to change the