For instance, you could ask for a set of results from the database as of
two hours ago. Flashback provided extra functionality by leveraging the rollback feature
that was already a core part of the Oracle architecture.
Since Flashback uses rollback segments, you can only flash back as far as the information
in the current rollback segment. This requirement typically limits the span of
flashback to a relatively short period of time??”younormally would not be able to roll
back days, since your Oracle database doesn??™t keep that much rollback information
around. Despite this limitation, there are scenarios in which you might be able to use
a Flashback Query effectively, such as going back to a point in time before a user
made an error that resulted in a loss of data.
The use of Flashback has increased as Oracle has added more flashback capabilities
to the database. Oracle Database 10g greatly expanded the flashback capabilities
available to include:
??? Flashback Database, to roll back the entire database to a consistent state
??? Flashback Table, to roll back a specific table
80 | Chapter 3: Installing and Running Oracle
??? Flashback Drop to roll back a DROP operation
??? Flashback Versions Query, to retrieve changes to one or more rows
Oracle Database 11g continues this expansion with the Flashback Transaction
feature, which can be used to reverse the effect of a transaction and any other transactions
that are dependent on it.
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