Blackouts allow Enterprise Manager administrators to suspend all data collection activity on one or more monitored targets. The primary reason for blacking out targets is to allow Enterprise Manager administrators to perform scheduled maintenance on those targets.
Login in OEM 12c and click on Enterprise à Monitoring à Blackouts
Click on “Create” to have a new blackout. If you have already existing blackouts and want a copy of same, you can use “Create like” too.
Fill blackout details and click on Add target. From the popup, select the target for which blackout needed.
Select the blackout options.
Select the scheduling options.
Review the information and you are all set.