Hi,

Can someone please guide me how to delete old alerts manually from SCOM Console under monitoring field.

I have closed the alerts manually but cannot delete them

Closed Alerts do not get deleted from SCOM console.

You can create a new Alert View for Active alerts, so that the closed alerts do not disturb you.

SCOM by default has a retention period to show the alerts in console. After that they go away into Data warehouse and then disappear from console. This is the  database grooming setting (seen under Administration tab) by default, it is 7 days.

Hope this helps.&

direct modifications of database information is not supported, with out MS intervention. The most you could do, is close the alerts, and change the retention period for alerts to 1 day. This setting is in the Administration tab, under settings, Grooming. the default is 7 days. change it to one day, wait a few days for the changes, then change it back to 7 days. 

there is a stored procedure that runs the grooming process, but I can't recall it off the top of my head.

hope this helps!

In SCOM design, user cannot delete any alert from the system except you manually delete the data table which is not recommend. The only option is changed the alert state into another state such as close state.
I recommend that you should use Active alert view to view alert which need to resolve and create another view which contains all alert or closed alert.
Beside, SCOM has grooming option which by default is 7 days to move alert from operations manager DB into operations Manager Data Warehouse such that you cannot see alert with more than 7 days but you can generate alert report using SCOM reporting.
Roger