Odds are you probably will have some machines where you can’t deploy the SCOM agent via SCOM console, or PowerShell, or some automated way, and you must install and configure the agent manually. Days/weeks/years go by and now you need to decommission that troublesome, manually installed agents Primary Managed Server. You go to the console and right click, and notice you cannot change the machines primary management server. Well that is because any manually installed agents SCOM/SQL disables this feature. Well, there is a workaround!
Launch SQL and run the following query against the OperationsManager database to get a list of all manually installed servers:
select bme.DisplayName from MT_HealthService mths
INNER JOIN BaseManagedEntity bme on bme.BaseManagedEntityId = mths.BaseManagedEntityId
where IsManuallyInstalled = 1
Now that you have determined which servers were manually installed, to re-enable the remotely manageable feature, run the following SQL query (against the OpsMgr DB).
You should note, this will re-enable this feature for all servers.
Now you should be able to change your machine or any manually installed machines primary management server!
Happy SCOM’ing =)