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Oracle9 i Flashback Query An Oracle White Paper March 2002
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Oracle9i Flashback Query Oracle9 i Flashback Query THE HUMAN ERROR CHALLENGE Human errors are one of the predominant causes of system failure. According to many studies, about 40% of application outages are caused by operator or user errors. These errors are extremely difficult to avoid and can be particularly difficult to recover from without advance planning and the right technology. Such errors can result in “logical” data corruption, or cause downtime of one or more components of the IT infrastructure. While it is relatively simple to rectify the failure of an individual component, detection and repair of logical data corruption, such as accidental deletion of valuable data, is a time consuming operation which causes enormous loss of business productivity. Most database products today do not offer any solutions to this problem leaving administrators with no option but to recover the database using a previous backup. This not only requires the database to be unavailable during the period of recovery but also leads to the loss of valid transactions if the database is required to be restored to a point in time in the past. INTRODUCING THE FLASHBACK QUERY Oracle9i introduces Flashback Query to provide a simple, powerful and completely non-disruptive mechanism for recovering from human errors. It allows users to view the state of data at a point in time in the past without requiring any structural changes to the database. Using Flashback Query, users can execute queries against a snapshot of data consistent to a point in time in the past either by specifying a wall clock time or a System Change Number (SCN). This capability allows users to correct logical errors, or simply view an old image of data, without any disruption in database services. Since Flashback Query can be executed without any administrator intervention, application developers can use this feature to build applications equipped with built in self-service error correction capability. Table data can be queried as it existed at a point in time. This lets applications query, compare, or recover past data without involving the DBA and without an expensive recovery operation. The current table data remains available to other applications throughout.
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Oracle9i Flashback Query HOW DOES THE FLASHBACK QUERY WORK? The Oracle database uses a version based read consistency mechanism by saving
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This note was uploaded on 07/15/2011 for the course ECO 2023 taught by Professor Mr.raza during the Summer '10 term at FAU.

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fbq - Oracle9i Flashback Query An Oracle White Paper March...

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