You can migrate service instances to another host if the current host does not meet requirements you have or if you need to take that host down for maintenance.
You cannot select a specific host to migrate to. The system selects the new host automatically. The system blocks the old host from having any new services assigned to it. You can remove a host from the blocked list through the Platform Management Console.
The system also migrates all service instances running on the same host. Migrating service instances takes the service down for a few moments.
You can migrate service instances that have the states Start or Run.