Your Oracle RAC database includes an Oracle database service identified by
DB_UNIQUE_NAME, if set, or
PDB_NAME, if not. This default service is always available on all instances in an Oracle RAC environment, unless an instance is in restricted mode. You cannot alter this service or its properties. Additionally, the database supports the following two internal services:
SYS$BACKGROUND is used by the background processes only
SYS$USERS is the default service for user sessions that are not associated with any application service
All of these services are used for internal management. You cannot stop or disable any of these internal services to do planned outages or to failover to Oracle Data Guard. Do not use these services for client connections.
You can explicitly manage only the services that you create. If a feature of the database creates an internal service, you cannot manage it using the information in this chapter.