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Oracle RAC Services are the primary mechanism for workload management in a RAC cluster. Rather than connecting directly to an instance (which bypasses all intelligent routing), applications connect to a named service, and Oracle manages where that service is active. Combined with Application Continuity (AC), services provide seamless failover that is invisible to most application workloads. Services Fundamentals A service is a named workload bucket with the following attributes: Preferred instances: Primary instances where the service is active. Available instances: Failover instances where the service moves if a preferred instance fails. Cardinality: SINGLETON (active on one instance at a time) or UNIFORM (active on all instances simultaneously). Role: PRIMARY or PHYSICAL_STANDBY (for Active Data Guard integration). # List all services in the cluster srvctl status service -d ORCL # Add a service for OLTP (preferred on instance 1, failover to instance 2) srvctl add service \ -d ORCL \ -s OLTP_SVC \ -preferred ORCL1 \ -available ORCL2 \ -cardinality SINGLETON \ -pdb PDB1 # Add a uniform service for read workloads (active on all instances) srvctl add service \ -d ORCL \ -s REPORT_SVC \ -preferred "ORCL1,ORCL2" \ -cardinality UNIFORM \ -pdb PDB1 srvctl start service -d ORCL -s OLTP_SVC srvctl start service -d ORCL -s REPORT_SVC Service-Level Performance Attributes Services can be annotated with performance and connection management attributes that affect how the Oracle Net listener and connection pool handle connections: ...