Advanced Flashback Features in Oracle Database 10g Release 2

In Oracle Database 10g Release 2, the flashback technology has been enhanced to provide greater flexibility with your recovery options. 10g Release 2 introduces two new features with Flashback Database and Flashback Table: flashback restore points and flashback across global database changes.

Flashback Restore Points

Flashback restore points are associated names that you define for a given point in time. Restore points, much like a transaction savepoint, allow you to flashback to a defined alias within your flashback history. By creating save points, users no longer have to investigate the SCN or timestamp of a specific operation before using the Flashback Table or Flashback Database feature. With restore points, you can create a custom snapshot of the database and later flashback to that specific point in time.

Restore points are maintained in the database control file for at least the number of days specified by the CONTROL_FILE_RECORD_KEEP_TIME setting, which has a default setting of seven days. When the number of restore points reaches the maximum value, the oldest restore points will simply age out.

If age is an issue for your restore points, you can elect to use a guaranteed restore point. Guaranteed restore points provide a guaranteed flashback point, never age out of the control file, and must be dropped explicitly when not needed. Keep in mind, however, that once a guaranteed restore point is created, all associated flashback logs that are needed to flashback to that specific point will be retained in the flash recovery area until you delete the guaranteed restore point.

To support the flashback restore points, 10g R2 introduced the CREATE | DROP RESTORE POINT commands, as well as new functionality within 10g Enterprise Manager (as showed here):

• To create new restore points (with or without the guarantee clause), do the following:

   SQL> create restore point before_patch_apply; SQL> create restore point before_patch_apply guarantee flashback database; 

  
  

• To use Flashback Database with restore points, do the following:

   SQL> flashback database to restore point before_patch_apply; 

  
  

• To use Flashback Table with restore points, do the following:

   SQL> flashback table flashtest to restore point before_patch_apply; 

  
  

• To drop restore points, do the following:

   SQL> drop restore point before_patch_apply; 

  
  

Flashback Across Global Database Changes

The second major new flashback feature with 10g Release 2 is the ability to flashback across global database changes. With this new functionality, you can use the Flashback Database feature to flashback through a database RESETLOGS operation, after a switchover/failover operation with your physical or logical standby database or even after physical standby database activation. Previously, when any of these global database changes occurred, all flashback log data was discarded and subsequently removed. With 10g Release 2, the flashback across global change support extends the functionality of the Flashback Database feature.

To flashback through RESETLOGS, do the following:

 SQL> shutdown immediate; SQL> startup mount; SQL> flashback database to before resetlogs; SQL> alter database open; 

Additional 10g R2 Views

Also with 10g Release 2, two new V$ views are introduced to provide greater manageability with your flashback environment:

• V$RESTORE_POINT. Details the specifics of user-defined database restore points such as SCN, incarnation, storage, time, name, and so on.

• V$FLASH_RECOVERY_AREA_USAGE. Details the specifics on flash recovery area disk space used.