EM 12c: How to Disable Diskmon and ONS Monitor from Enterprise Manager 12c Cloud Control to Stop Notifications: Message=ora.diskmon has 1 instances in OFFLINE State (Doc ID 2060296.1)

Last updated on FEBRUARY 27, 2017

Applies to:

Enterprise Manager for Oracle Database - Version 12.1.0.1.0 and later
Information in this document applies to any platform.

Goal

EM 12.1.0.4 Cloud Control monitors a RAC database host, on which critical alerts for DiskMon Offline are being generated for the High Availability Service.

Alert content similar to this is in the accompanying notification:

Host=urhost.com
Target type=Oracle High Availability Service
Target name=has_urhost.com
Categories=Error
Message=ora.diskmon has 1 instances in OFFLINE State
Severity=Critical
...
Key Value=resource_ora.diskmon.type_ora.diskmon
...

These errors are harmless for 11.2.0.3 and later database targets. 
The associated metric can be disabled to stop generation of alerts and notifications with the following procedure:

Solution

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