| Doubts on redo log files. [message #34036] |
Thu, 18 November 2004 18:33  |
Hari
Messages: 59
Registered: August 2000
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Member |
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Hi,
I am new to Oracle Architecture, could anyone plz help on the below mentioned basis q's.
1. Where does the redo log files are stored in the primary or secondary memory?
2. Does the system updates the redo logs each and every time when modify a record in a table?
3. What are Rollback Segments and how they are different from Redo Log files?
Regards,
Hari.
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| Re: Doubts on redo log files. [message #34047 is a reply to message #34036] |
Fri, 19 November 2004 03:54  |
William Robertson
Messages: 1643
Registered: August 2003
Location: London, UK
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Senior Member |
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1. They are files - they are not in memory?
2. Pretty much. They keep a record of changes that may need to be replayed when recovering from backups. You would restore the main backup, then apply the archived redo logs.
3. Rollback is undo - opposite of redo. It temporarily stores old values that may be needed for rolling back changes. Rollback/undo is also used by the database for read consistency: if another session makes changes without committing (or makes changes and commits them while your query is still executing), your session will pick up the original values from the rollback blocks.
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