High Availability Database SystemToday we are so dependent on information systems that system failures or data loss are increasingly intolerable. Sometimes the loss of critical data is directly linked to a business's ability to survive. This draws our attention to the reliability of the information system. According to reliability, it 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 form the background of most information systems, their availability is essential to the availability of the entire information system. Ensuring the continued availability of enterprise IT resources is one of the primary goals of today's database administrator (DBA). All the computing power in the world and secure/defensive application coding don't make a difference if users and customers can't access the resources they depend on to carry out their functions. If the database and servers that support the application are unavailable, it can cost the organization, both financially and in terms of reputation and goodwill. Depending on the nature of the organization and the type of application, the costs of downtime can be enormous. Not only databases, but also the Internet, have enabled collaboration and data sharing on a global scale by extending the reach of database applications within organizations and communities. This scope highlights the importance of high accessibility in information management solutions. Every small business and global enterprise has users all over the world who need access to information 24 hours a day. Even if it is not access to information, operations will remain at the middle of paper, which will result in the combination of people, processes and technology. A plan focused solely on technology will never achieve very high levels of availability, because many of the important factors that affect availability come from the interaction of people and processes. Preparing a suitable hardware and software platform is just the starting point. From this point on, high availability is the result of good planning and best practices combined with the right technologies. The need for high availability is determined by your business requirements and not by the presence of specific technology. While creating a highly available environment is always desirable, it is important to keep in mind that the higher the level of availability you require, the higher the associated cost. It is therefore essential to understand the level of availability your business needs..