2.10 Conclusion

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Clustering has a history that originates from the VMS days dating back to the early 1980s. In today's Internet-based computing environment, where every second of systems availability is very important for goodwill, reputation, customer retention, and continued business, it is an essential requirement that most application systems are implemented using hardware-clustered configurations. In this chapter, the various advantages that clustered configurations provide to the enterprise were closely considered. The way in which clustering works and how systems interchange information from one node to another was also investigated. The method of information interchange between systems is very important in order to deduce the availability of the members participating in the clustered configuration.

In an Oracle environment, a clustered configuration perfectly suits the implementation of RAC. RAC is a two or more node configuration running on a clustered operating system connected via a high-speed interprocess communication device (such as a Gigabit Ethernet interface) that shares a common set of storage devices. Each node contains an instance connected to a database that is configured on the shared storage device. Users or applications connect to either of these instances and perform Data Manipulation Language (DML) operations or make queries against the database. These nodes concurrently execute transactions against one shared database, while RAC coordinates the access from each node to the shared device, providing consistency and integrity. Such a configuration offers various benefits that any clustered configuration should provide such as scalability, high availability, transparency, etc.

In the next chapter we will discuss the basic concepts of Oracle. These concepts will help provide an understanding of the current technology and the new enhancements introduced in Oracle 9i. This chapter will help identify the suitable features of Oracle that could be utilized when designing an application system.

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