Explanation/Reference:
Explanation:
Oracle Real Application Clusters One Node is a single instance of an Oracle Real Application Clusters- enabled database running on one node in a cluster. It lets you consolidate multiple databases onto a single cluster and thereby adds to the flexibility that Oracle offers for database consolidation while reducing management overhead by providing a standard deployment for highly available Oracle Database editions.
Overview
Failover cluster protection for unplanned downtime

Online Database Relocation for workload management

Online database patching to reduce planned downtime

(C) Online upgrade to Oracle RAC for full scalability

Benefits
(F) Protection from unplanned database or system failures

(B) Rolling upgrades and patches for your OS and database

Standard management for highly available Oracle Databases

Online Databases Relocation for database virtualization

References: http://www.oracle.com/us/products/database/options/rac-one-node/overview/index.html