Topic: Database Administration >> Undo and Redo
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| rsreddy28 |
Posted: May 23, 2007 11:14:21 AM |
Total Post: 35
Joined: Mar, 2007
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Hello All,
What exactly is the difference between the UNDO and REDO. Can someone explain in detail abt them.
bYe,
Raj |
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 dipali |
| Posted: May 24, 2007 01:39:04 AM |  |
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Total Post: 31
Joined: Dec, 2006
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Dear raj,
The names themselve explains the meaning..
UNDO - un do the work i.e. To cancel (effect of) the work done..
REDO - Re - do the work i.e. Do the work again..
For example,
UNDO:
Suppose, in a transection, you have updated the address of perticular employee, and then later you realize, you changed it of Wrong emp. Then you need to undo that work.. In such case UNDO comes into picture..
REDO:
You are running a long query to update a table, the transaction is partially completed but not yet saved. During commit suppose some problem occurs because of which it cannot be completed. Then you have to redo that transection. Here REDO comes into picture..
In oracle,
UNDO is provided by undo segment feature. In 10g, oracle provides automation of undo management.
REDO is provided by redo log file..
Hope this helps you clear your concepts.
Regards..
Dipali
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