Oracle Real Application Cluster (RAC) is a "share-everything"
database architecture that can provide high availability and load
balancing. A typical configuration for an Oracle RAC contains two
or more Oracle RAC nodes that are clustered together and share the
same storage.
About this task
This figure depicts a typical RAC physical topology in a
cluster environment for the application server, and both the failover
and load balancing are enabled:

In the figure
above, the application server cluster consists of two members: cluster-member1
and cluster-member2. The Oracle RAC physical configuration contains
two nodes: rac-node1 and rac-node2. The RAC nodes can be located in
the same physical machine with the cluster members, or they could
be placed in entirely different machines. The actual placement does
not impact the fundamental qualities of the services provided by RAC.
To achieve both high availability and load-balancing, you can specify
the Oracle data source URL for both cluster members in the application
server with the required properties.