Oracle® Database SQL Language Reference 11g Release 2 (11.2) Part Number E17118-04 |
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Use the FLASHBACK
DATABASE
statement to return the database to a past time or system change number (SCN). This statement provides a fast alternative to performing incomplete database recovery.
Following a FLASHBACK
DATABASE
operation, in order to have write access to the flashed back database, you must reopen it with an ALTER
DATABASE
OPEN
RESETLOGS
statement.
See Also:
Oracle Database Backup and Recovery User's Guide for more information onFLASHBACK
DATABASE
You must have the SYSDBA
system privilege. A fast recovery area must have been prepared for the database. The database must have been put in FLASHBACK
mode with an ALTER
DATABASE
FLASHBACK
ON
statement unless you are flashing the database back to a guaranteed restore point. The database must be mounted but not open. In addition:
The database must run in ARCHIVELOG
mode.
The database must be mounted, but not open, with a current control file. The control file cannot be a backup or re-created. When the database control file is restored from backup or re-created, all existing flashback log information is discarded.
The database must contain no online tablespaces for which flashback functionality was disabled with the SQL statement ALTER
TABLESPACE
... FLASHBACK
OFF
.
See Also:
Oracle Database Backup and Recovery User's Guide and the ALTER
DATABASE
... flashback_mode_clause for information on putting the database in FLASHBACK
mode
CREATE RESTORE POINT for information on restore points and guaranteed restore points
When you issue a FLASHBACK
DATABASE
statement, Oracle Database first verifies that all required archived and online redo logs are available. If they are available, then it reverts all currently online data files in the database to the SCN or time specified in this statement.
The amount of Flashback data retained in the database is controlled by the DB_FLASHBACK_RETENTION_TARGET
initialization parameter and the size of the fast recovery area. You can determine how far back you can flash back the database by querying the V$FLASHBACK_DATABASE_LOG
view.
If insufficient data remains in the database to perform the flashback, then you can use standard recovery procedures to recover the database to a past point in time.
If insufficient data remains for a set of data files, then the database returns an error. In this case, you can take those data files offline and reissue the statement to revert the remainder of the database. You can then attempt to recover the offline data files using standard recovery procedures.
See Also:
Oracle Database Backup and Recovery User's Guide for more information on recovering data filesSpecify STANDBY
to revert the standby database to an earlier SCN or time. If the database is not a standby database, then the database returns an error. If you omit this clause, then database
can be either a primary or a standby database.
See Also:
Oracle Data Guard Concepts and Administration for information on how you can useFLASHBACK
DATABASE
on a standby database to achieve different delaysSpecify a system change number (SCN):
TO SCN
reverts the database back to its state at the specified SCN.
TO BEFORE SCN
reverts the database back to its state at the system change number just preceding the specified SCN.
You can determine the current SCN by querying the CURRENT_SCN
column of the V$DATABASE
view. This in turn lets you save the SCN to a spool file, for example, before running a high-risk batch job.
Specify a valid datetime expression.
TO TIMESTAMP
reverts the database back to its state at the specified timestamp.
TO BEFORE TIMESTAMP
reverts the database back to its state one second before the specified timestamp.
You can represent the timestamp as an offset from a determinate value, such as SYSDATE
, or as an absolute system timestamp.
Specify this clause to flash back the database to the specified restore point. If you have not enabled flashback database, then this is the only clause you can specify in this FLASHBACK
DATABASE
statement. If the database is not in FLASHBACK
mode, as described in the "Prerequisites" section above, then this is the only clause you can specify for this statement.
Specify TO
BEFORE
RESETLOGS
to flash the database back to just before the last resetlogs operation (ALTER
DATABASE
OPEN
RESETLOGS
).
See Also:
Oracle Database Backup and Recovery User's Guide for more information about this clauseAssuming that you have prepared a fast recovery area for the database and enabled media recovery, enable database FLASHBACK
mode and open the database with the following statements:
STARTUP MOUNT ALTER DATABASE FLASHBACK ON; ALTER DATABASE OPEN;
With your database open for at least a day, you can flash back the database one day with the following statements:
SHUTDOWN DATABASE STARTUP MOUNT FLASHBACK DATABASE TO TIMESTAMP SYSDATE-1;