How to Remove an Operations Manager 2007 R2 Gateway (Operations Manager Upgrade)
After you have replaced a System Center Operations Manager 2007 R2 gateway server that does not meet the minimum supported configurations for System Center 2012 – Operations Manager, you can remove the old gateways from the management group and uninstall the old gateway from the server. For more information, see Supported Configurations for System Center 2012 – Operations Manager.
You must first copy the gateway approval tool (Microsoft.EnterpriseManagement.GatewayApprovalTool.exe) from the \SupportTools directory of the Operations Manager 2007 R2 installation media to the management server, if it does not already exist.
To uninstall the gateway server
Log on to the gateway server to be removed with the Operations Manager 2007 R2 Administrators credentials.
In Control Panel, in Programs and Features, right-click System Center Operations Manager 2007 R2 Gateway, and then click Uninstall.
To remove a gateway from the management group
On the management server that was targeted during the gateway server installation, log on with Operations Manager Administrators credentials.
Open a Command Prompt window, and browse to the directory to where you copied Microsoft.EnterpriseManagement.gatewayApprovalTool.exe.
At the command prompt, run the following command, where GatewayName is the name of the gateway that you want to remove. Microsoft.EnterpriseManagement.gatewayApprovalTool.exe /ManagementServerName=<managementserverFQDN> /GatewayName=<GatewayFQDN> /Action=Delete
Open the Operations console to the Monitoring view. Select the Discovered Inventory view to see that the gateway server is no longer present.