[bbk4485]第二章Flashback Database 00

Objectives

After completing this lesson,you should be able to:

• Describe Flashback technology
• Configure Flashback Database
• Perform Flashback Database operations
• Monitor Flashback Database 

Flashback Technolog:Benefits

• Te Flashback technology is a revolutionary advantage in recovery.
• Traditional recovery techniques are slow.
  • The entire database or a file(not just the incorrect data) has to be restored.
  • Every change in the database log must be examined.
• Flashback is fast
  • Changes are indexed by row and by transaction
  • Only the changed data is restred.
• Flashback commands are easy.
  • No complex mulitple-step procedures are involved.

Flashsback Technology

Object Level	Scenario Examples	Flashback Technology	Depends On	Affects Data
Database	Truncate table; Undesired multiple changes made	Database	Flashback logs	TRUE
Table	Drop table	Drop	Recycle bin	TRUE
	Update with the wrong WHERE clause	Table	Undo data	TRUE
	Compare current data with data from past	Query	Undo data	FALSE
	Compare version of a row	Versoin	Undo data	FALSE
	Keep histrical transaction data	Data Archive	Undo data	TRUE
Transaction	Investigate and back out suspect transactions	Transaction	Undo/redo from Archive logs	TRUE