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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 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.
The Flashback Versions Query and Flashback
Transaction Query can be used in tandem to
determine the appropriate flashback time.
The SCN should always be noted before
issuing a FLASHBACK TABLE command.
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 Transaction Query is a
diagnostic tool to view the changes made to
the database at the transaction level. This
feature will help to 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. The Flashback
versions Query and Flashback Transaction
Query can be used in tandem to determine the
appropriate flashback time.
The dba_transaction_query view stores the
changes made by a transaction and the nature
of changes made during a specified time.
Using the transaction identifier or a time
range as part of the query, this dictionary
view provides information on changes made to
the database by any query at any time.
When there is insufficient undo data for a
transaction, the dba_transaction_query will
return a row with a value of UNKNOWN in the
OPERATION column.
The FLASHBACK ANY TRANSACTION system
privilege is needed to issue a query against
the dba_transaction_query view.
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