Oracle RAC One Node

In the latest version of Oracle Database (11g Release 2), there's a new option called Real Application Clusters (RAC) One Node. What is "One Nod开发者_高级运维e", and how does it differ from regular RAC?

Mogens Norgaard used to joke about "single node RAC" but now it actually exists!

Basically, One Node is running a RAC database on a single server, rather than across a cluster of servers. There is an Oracle white paper on the topic. Find it here. The money quote is:

"Oracle RAC One Node enables:
• Better server consolidation
• Enhanced protection from failures
• Greater flexibility and workload management
• Better online maintenance
In addition it allows customers to virtualize database storage, standardize their database environment, and, should the need arise, upgrade to a full multi-node Oracle RAC database without downtime or disruption."