Oracle Exam 1Z0-134 Topic 8 Question 3 Discussion

One server instance in a cluster that contains migratable servers acts as the cluster master and orchestrates the process of automatic server migration, in the event of failure.

Any Managed Server in a cluster can serve as the cluster master, whether it hosts pinned services or not.

Note: Any server instance in the cluster can serve as the cluster master. When you start a cluster that contains migratable servers, the first server to join the cluster becomes the cluster master and starts up the cluster manager service. If a cluster does not include at least one migratable server, it does not require a cluster master, and the cluster master service does not start up.