You can use the API to decommission a Platform Services Controller.
After converging an external Platform Services Controller node to an embedded Platform Services Controller node, decommission the original external Platform Services Controller. Decommissioning a Platform Services Controller shuts it down and removes it from the single sign-on domain.
If the Platform Services Controller is configured in an HA environment, you must use the host name of the load balancer instead of the Platform Services Controller host name and disable the virtual IP of the load balancer before decommissioning. If you encounter any complications with your environment, you can manually unregister nodes by using the cmsso-util unregister command as described in KB article 2106736.