High Availability Database SystemToday we depend so heavily on information systems that system disruption or data loss is increasingly intolerable. Sometimes the loss of critical data is directly related to the survival of a business. This draws our attention to the reliability of the information system. According to reliability, reliability is “the ability to avoid service failures that are more frequent and more severe than is acceptable,” and availability is one of the most important attributes of reliability. Since database systems represent the back end of most information systems, their availability is critical to the availability of the entire information system. Ensuring the continuous availability of computing resources in the enterprise is a primary objective of today's database administrator (DBA). All the computing power in the world and secure/defensive application coding makes little difference if users and customers cannot access the resources they depend on to perform their job functions. If the database and servers that support the application are unavailable, this can cost the organization both in monetary terms and in terms of reputation and goodwill. Depending on the nature of the organization and the type of application, the costs of service interruptions can be enormous. Databases and even the Internet have enabled global collaboration and data sharing by extending the reach of database applications across organizations and communities. This scale highlights the importance of high accessibility in information management solutions. All small businesses and global enterprises have users around the world who need access to information 24 hours a day. While there is no access to information, operations will be… middle of paper… so the combination of people, process and technology. A plan that focuses solely on technology will never achieve very high levels of availability because many of the significant factors that impact availability arise from the interaction of people and processes. Preparing the appropriate hardware and software platform is just the starting point. From then on, high availability will be the result of good planning and good practices combined with the appropriate technologies. The need for high availability is driven by business requirements, not by the presence of a specific technology. While creating a highly available environment is always desirable, it is important to remember that the greater the level of availability needed, the greater the associated cost. Therefore, it is critical to truly understand the level of availability your business needs.