Databases Reference
In-Depth Information
Flashback Query
Query returns results at a specific time or System Change Number (SCN) in the
past, using undo log information segments to reconstruct the data.
Flashback Version Query
Query returns versions of rows in a table over a specified span of time.
Flashback Transaction
Used for backing out an individual transaction and its dependent transactions by
utilizing undo data to its original state.
Flashback Transaction Query
Query returns all the changes made by a specific transaction.
Flashback Drop
When an object is dropped it is placed in a Recycle Bin, thus enabling a user to
simply un-drop the object to restore it.
Flashback Table
A table is returned to a specific past point in time.
Flashback Restore Points
Labels created by DBAs that map to points in time via timestamps or SCNs.
Flashback Database
Returns the entire database to a particular point in time and can be used instead of
point-in-time recovery in some situations.
Flashback Logs and Block Media Recovery
If data blocks are corrupted, enables retrieval of more recent copies of the data
blocks to speed repair.
Flashback Data Archive
Contains transactional changes made to every record in a table for the life of the
record. This capability is part of the Total Recall portion of the Advanced Com‐
pression option. To implement Total Recall, the Oracle Database creates a shadow
table to hold historical changes to the main table, freeing flashback from the limi‐
tations of a fixed size to UNDO space.
Which to Choose?
All the choices we've discussed in this chapter offer you some type of protection against
losing critical data—or your entire Oracle Database. But which of these is right for your
needs?
To quote the standard answer to so many technical questions, “it depends.” Export/
import strategies provide a simple and proven method, but the time lag involved with
