Re: rac vs dataguard

From: David Ballester <>
Date: Thu, 16 Jul 2009 20:19:11 +0200
Message-ID: <>


I'm agree with the points about application scalability, performance, etc... but what's about D&R? For performance you can always tune your application / Oracle / OS layer or add more nodes to the RAC but If you loose the primary site or the whole RAC ( big disaster or big human error ) you will must:

  • locate new hardware ( new host ) or make room on existing one.
  • Install software ( OS, Oracle binaries, patchsets... )
  • restore the whole database and recover as far as you can ( lost some of the newest redo logs ? )
  • Start to give service.
  • If some data was lost, tell your people to redo it again ( if it's possible )

With the Data Guard you have it done in a few minutes, and near zero data lost.

If you can survive without giving service for all the hours ( days? ) doing the previous steps, go on adding only new nodes to the RAC

But if service is important to you, you can spend a little more money on the iron ( is not so expensive this days ) and mount a Data Guard

You can mount a physical standby to protect the whole service and in the same host, mount a logical standby for reporting purpouses, using both of them the same binaries.

Define the resources for the physical standby as low as possible ( it only will be doing recovery ) and allow more resources for the logical one

If a big disaster occurs, you can activate the physical standby ( modifiying init to allow more resources ) and point the logical one to adquire data from the new primary, as part of your contingence procedure.

What's your opinion?



Received on Thu Jul 16 2009 - 13:19:11 CDT

Original text of this message