I had a very specific situation where I wanted to ignore an error from a specific agent. It turns out that it is easier and quicker to ignore a specific error using an OEM Metric. How? By using an agent parameter. adrAlertLogErrorCodeExcludeRegex.
How to do it?
In [AGENT_INST]/sysman/config/emd.properties, add a line with these parameters and the Regex to ignore the desired error or message.
Ignoring all ORA-700, for example, can be done by:
Now to ignore specific errors, for example, ORA 700 [kskvmstatact: excessive swapping observed]:
After this parameter inclusion, a restart on the agent is required.
This is also well-documented as per MOS EM 12c, 13c: How to Disable or Suppress OEM Alerts for Alert Log Error ORA-700 (Doc ID 2406779.1)
Hope this helps!