What is Oracle RAC ?

Oracle RAC is a shared database environment where multiple server nodes share DBMS instances, with shared concurrent access to disk. In November 2003, Gartner analyzed usage and implementation of early adopters of Oracle Database 9i (9i) RAC. At that time, RAC was reliable and provided increased scalability and availability; however, it was complex and required highly experienced database administrators (DBAs) to generate value; the complexity was a RAC inhibitor.

Fast-forward five years and multiple releases: Oracle has significantly improved RAC’s operational manageability and reduced its skill level for implementation and management. We interviewed more than a dozen RAC customers (most of whom implemented Oracle Database 10gR2 RAC) to gain an understanding of the business value of implementing RAC, and its pros and cons. Overall, we found significant value that justified the additional software costs.

However, RAC is not for every application. Here, we provide an analysis of benefits, strengths and challenges, along with guidance on when to use or not to use RAC.

By year-end 2003, Oracle had approximately 1,000 RAC production customers; today, it has more than 15,000, bringing RAC to the mainstream. Oracle has penetrated the midmarket as well, primarily through its Dell reseller agreement. Thus, Oracle’s investment in Oracle Database 10g (10g) manageability has reduced the complexity inhibitor. RAC runs on all Oracle-supported platforms, with Linux being its platform of choice. Approximately 30% of RAC implementations have deployed on Linux (and the percent is rising).

Oracle’s main RAC sales theme is selling a fully integrated software stack, including the operating system (OS) — Oracle Enterprise Linux, which is Oracle’s distribution of Red Hat Linux. While RAC licenses incur a 50% increment over a single-instance DBMS (see www.oracle.com/corporate/pricing/technology-price-list.pdf ), Oracle justifies the pricing due to reduced hardware costs (in addition to RAC benefits).

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