What is Primary Replica

Databases are replicated in order to get two complementary features: performance improvement and high availability. Performance can be improved when a database is replicated since each replica can serve read-only accesses without requiring any coordination with the rest of replicas. Thus, when most of the application accesses to the data are read-only, they can be served locally and without preventing accesses in the same or other replicas. Moreover, with a careful management, the failure of one or more replicas does not compromise the availability of the database.