Flashback Database: Single-command Recovery
Oracle has built Flashback features into 10g
that will replace the old recovery method of restoring data from tape backups. A fundamental change in 10g
is the shift in storage media from tape to disk. Mendelsohn explained that the use of tapes dates back decades to when tape was cheaper than disk. But now that the two media are nearly equal in cost, why not use disk, he argues. Tape recovery is linear, so administrators have to recover the database at a given point in time and roll the changes forward. Disk, on the other hand, enables random access recovery where only the needed data is restored.
Juan Loaiza, Oracle's vice president of systems technologies, describes the Flashback Database feature as "a rewind button for the database." A Flashback Log inside Database 10g acts as a continuous backup. It captures old versions of changed blocks, operating on only the changed data. An administrator can replay the log to restore a database and it restores only the changed blocks.
|Database 10g offers these Flashback recoveries at all levels: database, table, and row.|
offers these recoveries at all levels: database (Flashback Database), table (Flashback Table), and row (Flashback Row). The result is incremental recovery: the ability to go back only as far as necessary and to conversely go forward if you went too far. Loaiza sums it up by saying, "if it took you five minutes to make an error, it shouldn't take 50 hours to recover. It should take five minutes to fix."
All this internal intelligence promises reduced failover times with faster recognition and restart. Loaiza said, "we're trading disk space, which is cheaper these days, for downtime, which is expensive."
The approximately 2,000 attendees of Wednesday's keynote reacted enthusiastically to a demonstration of the new Flashback recovery features.
Oracle Database 10g is slated for release at the end of 2003.