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.
1 Enable RAC - On Unix this is done by relinking the Oracle software.  Make the software available on all computer systems that will run RAC. This can be done by copying the software to all systems or to a shared clustered file system.