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.
As the number of users and transactions increase, additional Oracle instances can be added to the Oracle database cluster to distribute the extra load. This document is an extension to my article Building an Inexpensive Oracle RAC 11g R2 on Linux - (RHEL 5).