For setup of oracle RAC infrastructure, we need to install Oracle Grid infrastructure and Oracle RAC licensed oracle products.
Oracle RAC coordinates and synchronizes multiple database instances to access the same set of database files and process transactions on the same database. And it runs above the Oracle Grid infrastructure on each RAC nodes.
And configuration of multiple node RAC database needs proper installation and configuration of Oracle Grid infrastructure and Oracle RAC products.
Oracle RAC is an Oracle database option, based on active-active shared everything database clustering architecture. On a database clustering architecture multiple database servers are grouped together and linked by a private interconnect network and work together as a single system.
In a shared everything architecture, each server in the cluster is connected to a shared storage. And in the active-active cluster, all the virtual servers in the cluster can simultaneously access the database files and all the workloads are distributed among the servers.
Oracle RAC is designed to provide scalability by allowing all the RAC instances to share database workloads.
Oracle Real Application Cluster(RAC) is an oracle database component(option) and the architecture of the cluster is based on a share everything architecture.
On Oracle RAC database, there will be multiple clusters of RAC database instances that have independent memory and background process but share the same storage and operate as a single system. The datafiles, controlfiles, redo log files and SPFILES of the clustered nodes are stored on the shared disks.
And Oracle RAC provides High availability incase of failure of cluster instances and scalability & load balancing purposes.