Real Application Clusters (RAC) is a clustering technology. Oracle RAC is a “shared disk” clustering solution that is significantly different from the architectures offered by Microsoft SQL Server and IBM DB2. Each node in an Oracle RAC cluster has equal access to all of the database data through a shared disk subsystem. Data is neither partitioned to specific nodes, nor replicated across nodes. A high-speed network interconnect allows each node to keep its in-memory view of data consistent.
An Oracle RAC configuration has the following architectural characteristics:
The following diagram illustrates the basic components of an Oracle RAC cluster.
A user should find an Oracle RAC database operationally identical to a database hosted on a single server. From top to bottom, the important features represented are: