Definition of irrigation. 1  1 : the therapeutic flushing of a body part with a stream of liquid. 2  2 : the watering of land by artificial means to foster plant growth.
Answer: To start with, Oracle Real Application Clusters (RAC) are a database system involving a configuration of multiple hosts or servers joined together with clustering software and accessing the shared disk storage structures.
On each of the hosts in the cluster, an Oracle Database instance is launched that uses the shared storage structures to provide the logical database objects. Thus, the multiple database instances provide a common database access for the users. Users can access the same database from any of the instances. RAC is a high availability solution, but care should be taken when deciding to implement RAC. Oracle's original Grid vision represented a pool of database servers, storage and networks in an inter-related resource platform.