Oracle Real Application Clusters

1.1 Introduction

Computer systems are central to the business strategy of any organization and are perhaps the most visible representation of the organization. This is the case in retail, wholesale, manufacturing, natural resources, financial services, publishing, online services, medical services, law, science, education, government, and military operations. As more advanced technologies become available, the role of the computer becomes more vital as businesses increasingly expect operations to continue 24 hours, 7 days a week throughout the year.

However, as with any equipment or technology, there are limitations on the capabilities of the computer system. The parts, or resources, of the computer (i.e., the Central Processing Unit (CPU), storage disk, disk controller, network card, etc.) are bound to experience failures or have processing power limitations. These resources are capable of handling only a certain workload and this capability is based on the workload that the system has been designed to handle. Increasing the workload of a system beyond this point results in decreased performance of the system.

A computer system comprises resources that are capable of accomplishing tasks. These capabilities and resources may be increased on the computer system in several ways. One of the main resources within a computer system is the CPU, which controls the computer through the interpretation and execution of instructions for the computer and is equal to the amount of computing performed in a unit of time. The addition of extra CPUs increases the capability of the system, which in turn helps to increase the computing power by a percentage of its current capacity.

The amount of data that can be shared between the memory and the storage device depends on the amount of memory and the amount of storage space allocated to the computer system. The availability of more memory means more data can be read from storage devices, assuming the disk subsystem is also capable of handling this increased I/O. This means fewer attempts to get data from disk and this may not provide benefits as required. Increase in performance, along with an increase in resources like CPU, storage, etc., may not provide proportionate benefits or at times may provide negative benefits.

The diminished return with increase in resources could be tied to the theory of economics known as the Law of Diminishing Returns. Applying this theory to the current analogy, the law states that for every additional unit of a resource that is consumed, the benefit that is derived from the additional resource increases at a decreasing rate. In other words, after a certain point with additional resources, no benefit in performance is derived.

In this chapter the discussions will be focused around the business requirements that drive the information technology in meeting its business goals of the enterprise.