Part 1 of this series gave you a gentle nudge on what Virtualization is and how you could use this technology to test and run all kinds of scenarios on your PC, before you started doing it in production. Contrary to what people say, you CAN deploy an Oracle RAC on VMware using the ESX Servers.

Before I introduce Oracle RAC, and to keep my articles interesting I will try to give a little pep talk so that I have your total attention. We will then talk about Oracle RAC and end up this article with some print shots of installing and setting up Windows 2003 Enterprise edition for RAC readiness, such as preparing RAW disks.

Do you identify yourself as being stuck in situations like these?

• Your application is becoming popular and is apparently getting *mission critical* all of a sudden.
• You have scaled-up your servers (meaning added as many processors, memory) to the maximum and you do not know how to contain the load anymore.
• Scaling out the load (spreading it across more machines), you have heard from some guys that you could have a bunch of "pizza boxes" to run your database.
• You are confronted with a choice and you want to cluster your databases? But wait a minute, is it clustering what you want? You do indeed want High Availability (HA), but don't you need something to balance out the load?

And, if your manager has given you an ultimatum to go out there and look for the best solution, this list of questions will keep growing. MSSQL offers a clustering option where you can make your database highly available but NOT load balanced! Many people are misinformed about this whole difference between high availability and load balancing; they are indeed two different things, VERY VERY different things! If you have been a managing a SQL Server cluster you know very well that you are merely managing an HA option in which you won’t even experience the failover scenario. So is mere HA good? No, I would say! You need a solution (and I mean in terms of a hardware resource) that also does the work for you while it is in its so-called passive state. That is exactly what Oracle RAC can do for you. It is a groundbreaking technology where you can do a whole lot of things, other than load balancing. So what is Oracle RAC?

Oracle RAC (Real Application Clusters)

Clustering technology is not new (actually a lot of things that we do today have found their origin long ago) , DEC introduced its VAX cluster and Oracle made its entry into the clustering world with its OPS (Oracle Parallel Server) which was a humble beginning. Did you know that oracle 9i had some 400 odd new features? Well RAC was one of them!

The RAC architecture has changed a lot since its inception so we will quickly check all the features from 9i up. In addition, as we go ahead with our series we will try to dissect the RAC understanding and move further into Administration, troubleshooting, management, performance, migration of single instance to Oracle RAC. I want to make sure that you really get on to playing on RAC. Also, note that with Oracle 10g onwards you do not need to buy an Enterprise Edition, you can very well deploy RAC with a Standard Edition. Upon writing this article, I also read somewhere that Oracle will be releasing its Express Edition (beta is already released) which will be totally free and lightweight. Who knows, someday you may REALLY be RACing on PC’s!

Now let’s take a quick look at the latest features of Oracle RAC in the latest product 10g Release 2.

New features in Oracle 10g Release 2

• Cluster Ready Services are called Oracle Clusterware now. It has also grown in size; it is about 180MB. You can also use it for Single Instance databases.
• Oracle Clusterware High Availability API Support available.
• Cluster Verification Utility (CVU), handy if you want to check the cluster features such as node availability, administration, etc.

Use these commands before Clusterware installation for system verification

cluvfy comp sys [ -n node_list ] -p { crs | database } }  
[-r { 10gR1 | 10gR2 } ] [ -osdba osdba_group ] [ -orainv orainventory_group ] [-verbose]

• Cloning the Clusterware and Nodes

  The advantages are obvious. You can install once and deploy anywhere--be it development to production or production to test.

• Oracle Load Balancing Advisory

  This advisor monitors the load across the cluster and advises appropriately to the AWR (automatic workload repository) and a Fast Application Notification (FAN) event is published.

• Oracle RAC Runtime Connection Load Balancing
• Oracle Fast Connection Failover (FCF)
• Watch out for these deprecated views (Since 10g Release 1):
  • GV$CLASS_CACHE_TRANSFER and V$CLASS_CACHE_TRANSFER
  • GV$CACHE_LOCK and V$CACHE_LOCK
  • GV$FALSE_PING and V$FALSE_PING
  • GV$FILE_CACHE_TRANSFER and V$FILE_CACHE_TRANSFER
  • GV$GC_ELEMENTS_WITH_COLLISIONS and V$GC_ELEMENTS_WITH_COLLISIONS
  • GV$TEMP_CACHE_TRANSFER and V$TEMP_CACHE_TRANSFER
  • GV$LOCK_ACTIVITY and V$LOCK_ACTIVITY
• Changing the Archiving Mode

  You do not have to modify the CLUSTER_DATABASE parameter to change the archiving mode in RAC. You can do it while the database is mounted (and not open)!

• Oracle 10g Release 2 allows for dynamic RMAN channel allocation for RAC environments.
• Multiple Clusterware files: Clusterware file redundancy is achieved by maintaining two copies of the Oracle Cluster Registry (OCR) and three or more copies of the voting disk files thereby eliminating the single point of failure and the continual dependency on 3^rd party support.

AS you have seen, the 10g version has loads of new features and I particularly like the cluster verify and the Cloning Utility. Please read the documentation for more on new features.

OK, now having given this gentle introduction to the Oracle RAC (I know, there is a lot more to it than meets the eye but we’ll cover that later).

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