| aliai |
Posted: May 13, 2008 02:17:01 AM |
Total Post: 11
Joined: Apr, 2008
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| Any one can clear my doubts whats the diff b/w undo and redo if uncommited changes goes to redo log buffer then whats the purpose of undo? |
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 Gitesh |
| Posted: May 13, 2008 02:36:09 AM |  |
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Total Post: 322
Joined: May, 2005
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Redo contains each and every DML/DDL statements with commit and rollback information.
Undo contains only before image of data block which uses in any DML operation.
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| http://shaharear.blogspot.com |
| Posted: May 13, 2008 03:14:45 AM | |
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Total Post: 79
Joined: Apr, 2008
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please go through
http://www.ss64.com/orasyntax/9redo.html
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| dbavinod |
| Posted: May 13, 2008 04:07:54 AM | |
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Total Post: 90
Joined: Sep, 2006
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Oracle redo logs are literally a transcript of what goes on inside the database and contain a mine of information
Oracle Database generates an undo and a redo entry for each change made to the database. In simple terms, an undo entry provides the values of data stored before a change and the redo entry provides the values of data stored after a change. The redo entries are written to log buffers in the system global area (SGA) whenever a change occurs. The log writer (LGWR) process then writes the redo entries to the online redo logs,
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| jogi |
| Posted: May 15, 2008 01:33:54 AM | |
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Total Post: 21
Joined: Jul, 2007
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redo is nothing but redolog file which records all the changes made to the database.
Undo is the previous image of the redolog files.'
cheers
Prasad
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