Database Reference
In-Depth Information
Chapter 14
RAC One Node
by Syed Jaffar Hussain
RAC One Node, widely acknowledged as “the always-on single-server database,” was first introduced with Oracle 11gR2
(11.2.0.1) Enterprise Edition to render High Availability solutions for single-instance databases. RAC One Node is a
single-instance RAC database that runs on a single node in a cluster at any given point. The core objective of RAC One
Node features is to minimize the impact of single-instance database availability during planned and unplanned server
outages through its exceptional online database migration capabilities. In addition, with the online database conversion
capabilities, a RAC One Node database can easily be scaled out to a fully functional traditional RAC database.
The Big Picture
RAC One Node typically provides a traditional cold-failover solution to confront unplanned database server outages
by automatically starting up the impacted database, either on the same node or on a preconfigured candidate node
in the cluster. RAC One Node provides an option for online database migration between active nodes of a cluster for
any prolonged planned database or server maintenance outages. Also, when a node with RAC One Node existence
becomes overloaded, the database can be easily moved online to another node in the same cluster. Relocating a
RAC One Node database instance from one node to another in a cluster requires no application downtime, as it is
performed absolutely online. Moreover, when an application workload ramps up over time and business demands
additional database resources to handle the workload efficiently, the RAC One Node database can be easily and
quickly upgraded to a multinode, fully functional, and traditional RAC database without any application downtime.
RAC One Node fully supports Oracle Data Guard, and runs on Exadata machines and Oracle virtual machines
(VM). With RAC One Node, multiple single-instance databases can be consolidated into a single server with less
overhead. In a nutshell, RAC One Node reduces planned & unplanned database outages and significantly improves
overall database availability with its unique online migration capabilities.
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Note
RAC One Node is not supported on third-party clustering solutions.
Some of the key benefits of RAC One Node are as follows:
•
Easy and fast online database conversion to a traditional RAC database to meet and satisfy
increased workload demands
•
Quick online database migration from one node to another node in a cluster during planned
software/hardware downtimes and when the node becomes overloaded
•
Uninterrupted single-instance service, except during unplanned outage
