ORACLE RAC

Let me start off with Oracle RAC (Real application cluster). I am sure if you are an Oracle professional, you must have some experience or knowledge about Oracle RAC technology. Oracle RAC is more refined or matured product of its predecessor “Oracle parallel server” which started off in the version 7 of oracle. The parallel server technology at that time is not used by a whole lot people and had some real drawbacks.

Oracle parallel server has improved a lot since it started off and is getting better with each version. In oracle 8i version of the parallel server, Oracle has introduced a new feature called “CACHE FUSION”, which I feel is significant achievement/turning point. This feature helps the other participating instances in the parallel server environment to read/share the SGA (system global area) of the other instances. In previous versions of RAC oracle has to write the data to disk first, before it becomes available for other participating instances.
In Oracle 9i this product officially received the name Real Application Cluster (RAC). In my experience I would consider Oracle 9i version of RAC as a real parallel database with many features. The installation and administration process has simplified a lot. The evidence is more and more people started using oracle 9i RAC database. It was difficult to get an Oracle professional in Oracle 8i days who posses oracle parallel server experience. It’s not the case after oracle 9i RAC was introduced.

Oracle has introduced many new and revolutionary changes to the RAC product in the 10g version. The most significant is the introduction of CRS (Cluster Ready Service) which is Oracle’s own cluster ware. The thing I like with CRS is that, it can work with other third party clustering tools, if you don’t prefer to use CRS as clustering software. Oracle has also provided many tools for administration ease such as “srvctl” “crs_stat” etc. I think Oracle still has a long way to go. I was stuck with a simple issue after the RAC build and it took almost 2 months to resolve, there is no good utilities to debug some of the common issues even in 10g.

I haven’t really got a chance to put my hands on the Oracle 11g RAC, but sure will get to it soon. I have gone through some of the Oracle 11g manuals and have some book knowledge. Unless I try them out, I don’t feel comfortable taking about it.

More and More people started using RAC databases and the demand will increase over the time. If you are already a DBA with oracle experience, it doesn’t take much time to get acquainted with the RAC system. If you are in search of an Oracle DBA job, experience in managing RAC databases is an added advantage.

I'll be discussing in detail more on the Oracle RAC installation and setup soon. Stay tuned.