Real Application Cluster (RAC)

A Real Application Cluster (or RAC) is a environment in which multiple instances are linked by an interconnect. These instances all share the same database. This makes it possible to provide high availability, scalability and reduncy during failures.

Advantages of RAC:

• Fast node and instance failover (seconds)
• Connection and service failover across instances
• Node, instance and service switchovers can be planned
• Rolling patch upgrades

Typical RAC environments use symmetric multi processors.

RAC combines the two best elements of traditional clustering:

• shared nothing
• shared disk

RAC promises to make scaling easy by just adding a new node to an existing cluster. The application needs not be touched at all in order to make use of the new node. Nodes can be addes with the Oracle Cluster Manager.

RAC supports

• shared SCSI
• NAS
• SAN (Storage Area Network)