Title: High availability of the database systemThe high availability of the database system, in which unplanned downtime does not exceed seconds or only relatively few minutes per year, It is often a key focus in a company's data protection strategies and one of the cornerstones of business continuity. However, an overemphasis on high availability can lead to problems with data retention (all the money is spent on keeping systems up and very little on preventing data loss when they go down), with data responsiveness ( failure-resilient storage often fails to restore them as quickly) and data privacy (all the money is spent on keeping systems up and very little is spent on protecting data from unauthorized exposure). As a result, an organization may not achieve its true data protection goals and will likely spend more than necessary on data protection. Figure 1: High availability depends on the entire IT infrastructureHigh availability depends on the entire IT infrastructure (Figure 1) and not just on the storage part of that infrastructure. For example, if a network is unavailable for any reason, the data on the disk array that an application accesses over that network is also unavailable, even if the disk array is functioning perfectly. All applications do not have the same level of availability. However, for applications requiring high availability, all relevant components of the IT infrastructure must be tuned to the same relative level of protection. Otherwise there is the problem of the weakest link in the chain. Under normal circumstances it is unlikely that your entire IT infrastructure was designed for high availability. High availability is a relative term. In reality there are increasingly higher levels of availability, w...... middle of paper ......d to user requests will allow you some time to change systems. The bottom line is that you need to plan the necessary infrastructure to ensure that all application components use the high availability features built into Application Server 10g and Real Application Cluster Database 10g. SQL Server 2008 has several high-availability technologies; Windows failover clustering provides protection against server failure; database mirroring and log shipping provide protection against site and database failures; and others. Selecting the appropriate high-availability technologies requires that your organization's availability needs and budget match the capabilities and requirements of the different high-availability technologies. Different technologies provided by SQL Server 2008 are designed to provide different levels of data availability and protection.