Wednesday, April 7, 2010

Oracle RAC One Node - What is it?

I am reviving my blog after a long time. Hope I will be much regular. Some of my posts have been popular and received good feedback. Thanks to all of you who visited this blog and I am glad that the information has been useful.

I was looking for some information on Oracle RAC One node, early this year and did not find much. I thought to do a post on my views/opinion on this latest option introduced by Oracle. I am yet to get hands-on with this option. Please leave your comments/feedback if you have different opinion/experience with this feature Or let me know if this post has any wrong/misleading information. It will be a healthy discussion.

What is Oracle RAC One Node?

Oracle introduced a new option called RAC One Node with the release of 11gR2 in late 2009. This option is available with Enterprise edition only. Basically, it provides a cold failover solution for Oracle databases. It’s a single instance of Oracle RAC running on one node of the cluster while the 2nd node is in a cold standby mode. If the instance fails for some reason, then RAC One Node detects it and first tries to restart the instance on the same node. The instance is relocated to the 2nd node in case there is a failure or fault in 1st node and the instance cannot be restarted on the same node. The benefit of this feature is that it automates the instance relocation without any downtime and does not need a manual intervention. It uses a technology called Omotion, which facilitates the instance migration/relocation. “RAC one” is Oracle’s answer or solution to OS clustering solution like Veritas Storage Foundation, Sun Solaris cluster, IBM HACMP, and HP Service guard etc.


Its Oracle’s attempt to tie customers to a single vendor by eliminating the need to buy 3rd party OS cluster solutions. First, it introduced Oracle Clusterware with 10g and stopped the need to rely on 3rd party cluster software and now it intends to conquer the rest who are still using HACMP, Sun Solaris cluster etc. for cold failover.


The Oracle RAC One node provides the following benefits:

•         Built-in cluster failover for high availability
•         Rolling patches for single instance database
•         Proactive migration / failover of the instance
•         Live migration of instances across servers
•         Online upgrade to RAC

The rolling upgrade is really useful. Upgrade to the OS, and Database can be done without any downtime unless upgrade requires some scripts to be run against the database. With RAC One Node, the DBA’s and Sys admins can be proactive and migrate/failover the instance to another node to perform any critical maintenance activity.

What it's not suited for

According to me the RAC one node is not a viable or recommended solution in the following scenarios:

•         To load balance unlike regular RAC
•         A true high availability solution
•         As a DR solution; Data guard best suits the bill
•         For mission critical applications


It is definitely not FREE. Oracle has priced RAC one at par with Active Data Guard. The RAC One node is priced separately and costs $10,000 per processor as against $23,000 for regular RAC. The licensing cost is required for ONE node only (in a 2-node setup). RAC one node is eligible for 10-day rule, allowing a customer to migrate to another without the need to buy additional license up to 10-days in a calendar year. People arguing against paying a license fee for resources they are not using will still lament.


I am still not very convinced on the usefulness of RAC one node. I think customers invest in RAC for their mission critical applications and achieving high availability and load balancing at the same time. Those who don’t go for RAC rely on Data Guard and now with 11g, on Active Data Guard. So don’t see a huge requirement for RAC One except seamless failover within a data center. The licensing is a bit disappointing; they are making clients pay $10 K. Moreover RAC is free with Standard edition though one doesn’t get enterprise features and limited to 4 CPU sockets only. So, thinking RAC One will be popular among customers who are currently using standard edition and want to switch to enterprise will be wrong. However, this is still a very new feature and as more people adopt it, we will get more clarity on its’ usability. I am planning to do a POC on it and would publish the installation steps and any findings (goods things and not so good things) of my POC.
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Aman Sharma said...

Very nice Siba! As you rightly put, the move is to kill the o/s level clustering done by the shops. I haven't got my hands yet on it but I hope, very soon , I shall see it in action! I shall post some more insights at that time!

Hope you are going to be more active now on the blog :-) .


d said...

i like this

sonu said...


Nice content.

Have you implement RAC one node. if yes then pls. provide screenshto or some more details on this.

I am plannign to install RAC one node but don't understand from where to start.

Initially I have two VMs on OVM2.2 but when read about RAC one node I want to know how its actually work?

Could you please inform me that to implement RAC one node do I need to install clusterware on single or on both the nodes?


Vladimir said...

Excellent article on one node RAC. Unfortunately, these are hard to come by. Also, I am sorry to inform you that is outdated. Even the ones for 11gr1 are outdated.
If you want something more hands-on, try these:

You can find more demos (including dataguard, goldengate, streams) there at

Vladimir Grigorian

Vladimir said...

Excellent article. I am sorry to inform you that is outdated. Even the ones for 11gr1 are outdated.
If you want something more hands-on, try these:

You can find more demos (including dataguard, goldengate, streams) there at

Vladimir Grigorian

Rafi said...

Nice Article........

Best regards,


Sabi Miri said...

I think that, this article gives Architects/DBAs a good high level overview of RAC One Node. In addition Licensing info is well appreciated. Thank you!
Kind Regards,


Sabi Miri said...

I think that this article gives Achitect/DBA community a good high level overview of Oracle RAC One Node. In addition, Licensing information is most of the time neglicted and obscure, so thank you for sharing it with us! Well done.

Warm Regards,


Dave Lawn said...

Thinking of using it as a 1st step towards a 'proper' RAC solution. It claims to be easily portable to this.

Mark Malakanov said...

>Those who don’t go for RAC rely on >Data Guard and now with 11g, on >Active Data Guard.

With Data Guard latest transactions can be lost if not transmitted from primary node. RAC One node preserves all committed transactions.

License-wise Data Guard is more expensive because it requires to license RDBMS on secondary (even passive) node.
RAC One Node does not require RDBMS license for secondary passive node.

Compare failover solutions for two 1 processor nodes:

RAC One Node - RDBMS Oracle EE for primary node ($47.5K), RAC One Node ($10K) = $57.5K

Data Guard - RDBMS Oracle EE for primary and secondary nodes ($47.5K * 2) = $95K

Active Data Guard - RDBMS Oracle EE for primary and secondary nodes ($47.5K * 2), ADG (10K) = $105K

Pavan Peri said...

Good understanding points, given satisfactory points ....Please educate the same way for other new upcoming terminology.

Pavan Peri said...

Good --very well understood the difference between RAC one Node and RAC. Thanks

Pavan Peri said...

Very Good Article