In a replicated data cluster no shared disks exist. Instead, a data replication product synchronizes copies of data between nodes or sites. Replication can take place at the application, host, and storage levels. Application-level replication products, such as Oracle DataGuard, maintain consistent copies of data between systems at the SQL or database levels. Host-based replication products, such as Veritas Volume Replicator, maintain consistent storage at the logical volume level. Storage-based or array-based replication maintains consistent copies of data at the disk or RAID LUN level.
Figure: Shared storage replicated data cluster shows a hybrid shared storage and replicated data cluster, in which different failover priorities are assigned to nodes according to particular service groups.
You can also configure replicated data clusters without the ability to fail over locally, but this configuration is not recommended.