OF 8 Oracle9i lets users correct mistakes by providing them the ability, through SQL, to view change history and back out of the error by restoring data as it existed before the error. One of the more useful features in Oracle9i is called DejaView, which lets data be queried from a particular point in the past.
Users select the date and time to be viewed.
Any subsequent SQL query they execute will operate on data as it existed at that particular point in time. Obviously, query performance depends on the amount of data being queried and the number of changes to the data that must be backed out. Administrators specify how long an undo will be kept in the database. Several improvements in Oracle9i focus on improving database performance with respect to E-business application scenarios. Improved Java garbage collection, better native compilation, increased object sharing, and session pinning have improved internal Java application performance.