The Flashback Archive Data Feature in Oracle Database 11g overcomes most of the limitations in the previous versions. It automatically tracks every single change made to the data stored inside the database and maintains a secure, efficient and easily accessible archive of historical data. The captured historical data can be retained for as long as the business demands and is easily accessible using standard SQL constructs. Historical data tracking can be enabled on both existing and new tables instantaneously and more importantly, in a completely application transparent manner.
Implemented natively inside the database, Flashback Data Archive presents a high performance, storage optimized solution with a centralized management interface for satisfying data retention and change control requirements for organizations. The primary advantages of using Flashback Data Archive for historical data tracking include:
1. Application Transparent : Enabling historical data capture on one or more tables can be done instantaneously with no or minimal application changes. Customers can therefore use this feature to capture historical data for both packaged as well as home grown applications.
2. Seamless Access : Historical data can be easily accessed using familiar Flashback SQL constructs. Flashback Data Archive includes support for Flashback Queries. Applications can seamlessly query the history of table data, as it existed in different points in time. No special snapshots need to be taken to take advantage of this feature.
3. Security : Historical data, once generated, is immutable to all users. This is enabled out-of-the-box and no special or extra setup is required. Access to the internal history tables is restricted to reads only. No DML operations are allowed to users, including administrators. Applications need not query the internal history tables directly as seamless access is provided through the Flashback Query mechanism.
4. Minimal performance overhead : Regular user transactions will see negligible impact. Flashback Data Archive employs a lightweight mechanism to mark DML operations on tracked tables for archiving. The actual history generation and archiving is done asynchronously through a background process as explained later
5. Storage Optimized : The history data is internally partitioned and highly compressed to reduce the storage footprint. Flashback Data Archive employs a highly efficient compression scheme to compress the internal history tables based on a range-partitioning scheme. Both compression and partitioning in flashback data archive are managed automatically and require no special administration.
6. Centralized Management : Flashback Data Archive provides a centralized and policy-based management interface to automate a number of ongoing administrative tasks. With Flashback Data Archive, you can easily group tables and set a common retention policy. New tables will automatically inherit the retention parameter from the flashback data archive it is a part of. Oracle will automatically purge aged-out history data for all tracked tables based on the specified retention. This frees up the administrator from the repetitive management of history data and avoids costly errors associated with manual maintenance such as purging wrong history.