Question
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 Node", and how does it differ from regular RAC?
Solution
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."