Archive for September, 2012|Monthly archive page

Curb Your Enthusiasm: Database Virualization

In Cloud, Consolidation, DBA, Oracle database on September 29, 2012 at 00:38

Larry David says: “You write about what you know”.

RAC is one of the most controversial topics among database experts.

An extremely interesting article, called Database Virtualisation: The End of Oracle RAC? was published this month (September 2012) on

I recommend it to every Database Architect, DBA and Developer! Along with the comments after it. Plus its links to related papers and blogs.

Another interesting post on the RAC issue, entitled To RAC or not to RAC and its sequel To RAC or not to RAC (reprise part 2) is worth reading as well.

To make it simple, let me quote

“The biggest disadvantage is that you are adding more complexity to your database architecture. With more complexity comes a higher cost in maintaining and administering the database along with a higher chance that something will go wrong.

The second biggest disadvantage is the cost associated with RAC. Oracle is touting RAC on Linux as a way to acheive cost savings over large Unix servers. With RAC, the costs shift from hardware to software as you need additional Oracle license fees. The big question is will this shifting of costs result in any cost savings. In some cases, yes, and in other cases, no.”

Which would be the third big disadvantage of RAC? I say the bugs! Or let me put it more mildly: RAC just develops random features. And hunting errors in RAC is complex, right? On top of ORA-600, we now have even ORA-700.

Let me offer you some quotes from the RAC debate on

  • “Then there are the younger DBAs looking to gain more experience, who may say that RAC is a great thing. Secretly that might not necessarily be true but they want the experience.”
  • “We also see that there are “no application changes necessary”. I have serious doubts about that last statement, as it appears to contradict evidence from countless independent Oracle experts.”
  • “Complexity is the enemy of high availability – and RAC, no matter how you look at it, adds complexity over a single-instance implementation of Oracle.”
  • “At no time do I ever remember visiting a customer who had implemented the various Transparent Application Failover (TAF) policies and Fast Application Notification (FAN) mechanisms.”

  • So, is Database Virtualization the answer?

    I think that database virtualization is a concept that has been misunderstood and most of all wrongly defined by many. According to the Oxford Dictionarries, in Computing, virtual means something which is not physically existing as such but made by software to appear to do so.

    Decide for yourself what is then a virtual database. At least, it is not a database built in a virtual server! I did discuss that at the Oracle ACE Director Product Briefing at Oracle headquarters this week with world’s top database experts and what can I say: the topic is highly controversial.

    Let us go to the Oracle Database Documentation Library and search for virtualization. Here is the result:

    And you will get the same result for virtualisation (with “s”).

    So, what do we get? Not much.But let’s continue reading:

  • Database Virtualization Part 2 – Flash Makes The Difference
  • The Do’s And Don’ts Of Virtualizing Database Servers
  • Disadvantages of Virtualization, What’s Your Opinion?
  • Virtualization Best Practices
  • Let us wait for next Oracle’s database release and see what it will offer us.