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Oracle flashback is a powerful tool for
auditing and recovering Oracle databases
from user-error. Let's take a
closer look at Oracle flashback from the
bestselling Oracle10g book
Oracle Database 10g New Features
by Mike Ault, et. al.
Here is a list of 10g
extended flashback features:
Flashback Database
- This feature introduces the FLASHBACK
DATABASE statement in SQL. It allows you
to quickly bring your database to a
prior point in time by undoing all of
the changes that have taken place since
that time. This operation is fast,
because you do not need to restore the
backups. This results in much less
downtime following data corruption or
human error.
Flashback Standby
Database -
This flashback feature improves the
switchover and failover time of a
standby database. You no longer need to
specify a log apply delay, because you
can now roll back the standby database
if an error occurs on the primary and is
propagated to the standby.
Flashback
Reinstantiation
- This flashback feature reduces the
need to reinstantiate the old primary
database following a failover. This in
turn lets you restore full resiliency
after a failure more quickly. You can do
this by using the SQL statement
FLASHBACK DATABASE to roll back the
primary database in time to synchronize
with the standby database.
Flashback Drop
- Oracle now provides a way to use
flashback to restore tables that were
dropped accidentally.
Flashback Table
- This feature introduces the FLASHBACK
TABLE statement in SQL, which lets you
quickly recover a table to a previous
point in time without restoring a
backup.
Flashback Row History
- Using undo data stored in the
database, you can now use flashback to
view the changes to one or more rows
along with all the metadata of the
changes.
Flashback Transaction
History - This
flashback feature lets you examine
changes to the database at the
transaction level. With flashback
transaction history, you can diagnose
problems, perform analysis, and audit
transactions.
About Oracle Flashback
Transaction Query
One of the important new features of
Oracle Database 10g is the Flashback
Transaction Query. It is a diagnostic
tool to view the changes made to the
database at the transaction level. This
flashback feature will help diagnose
problems, analyze and audit
transactions, and recover from user or
application errors. The undo SQL
generated by the flashback transaction
query can be used to rollback the
changes made by a transaction.
Oracle10g provides the ability to easily
reconstruct SQL statements that have
been executed by SQL statements.
Previously, you would need to use Log
Miner to generate SQL redo statements
that could be used to replicate SQL
statements executed in the database.
Now, Flashback Transaction Query can be
used to reconstruct the SQL statements
used to make changes in the database,
and those that can be used to undo the
change.
Flashback Transaction Query uses an
indexed access path to get to the undo
data. It is faster than the LogMiner,
which mines the redo log files to obtain
the undo information.
Flashback Table
The flashback table command allows you
to flashback an Oracle table based on
timestamp or database SCN. All flashback
table operations must be at the
beginning of any transaction and
flashback table operations are not
supported for the SYS user.
The Flashback Table allows the DBA to
recover database tables to a specific
point in time without restoring from a
backup. With this feature, the data in
the tables and all associated objects
including indexes, constraints, triggers
etc. are restored. This statement is
executed as a single transaction. All
the tables must be flashed back
successfully or the entire transaction
is rolled back.
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