Oracle Database Online Documentation 12c Release 1 (12.1)
ClusteringClustering relieves users from concerns about where data resides and which computer processes their requests. Users request information or computation and have it delivered - as much as they want, whenever they want. For the DBA, the grid is about resource allocation, information sharing, and high availability. Oracle Database with Real Application Clusters and Oracle Clusterware provide the infrastructure for your database grid. Oracle Automatic Storage Management (Oracle ASM) provides the infrastructure for a storage grid. Oracle Enterprise Manager Grid Control provides you with holistic management of your grid.
Oracle Real Application Clusters
Oracle Real Application Clusters enables a single database to run across multiple clustered nodes in a grid, pooling the processing resources of several standard machines.
Oracle Clusterware is a portable cluster software that allows clustering of single servers so that they cooperate as a single system. Oracle Clusterware also provides the required infrastructure for Oracle Real Application Clusters (Oracle RAC). Oracle Clusterware also enables the protection of any Oracle application or any other kind of application within a cluster.
Oracle Automatic Storage Management
Oracle ASM provides a virtualization layer between the database and storage. It treats multiple disks as a single disk group, and lets you dynamically add or remove disks while keeping databases online.