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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Redo Logs Question
Tom,
My general rule of thumb in determining how large the redo logs should be is to size them so that they fill no sooner than 20 minutes apart. This is *not* a hard rule by any means. 20 minutes gives log writer plenty of time to clear them so that they can be ready for the next go-around. You can make more room available by making them much larger. The trade-off is in database restore/recovery time (the larger the redo logs, the larger the archive logs, the longer it will take to process each one during recovery).
In your case, lets say we try and calculate the 20 minute rule. Right now, you are filling 5k every 90 seconds. To extend this to 20 minutes, you need to:
20min*60sec=1200sec/90sec=13*5k=65k.
If you increase your redo logs to 65 k, you should switch every 20 minutes.
You really need to get to the backup and recovery class. It is the basis for determining just these type of questions. If I were you, I would get back to your management and stringly urge them to get you to a class ***WELL BEFORE*** you get into production.
Hope this helps
Tom Mercadante
Oracle Certified Professional
-----Original Message-----
Sent: Monday, December 31, 2001 10:20 AM
To: Multiple recipients of list ORACLE-L
Here is the background of the stiuation I am facing.
We are piloting a application that uses a hybred store and forward system to aggregate all of our disparate student data into one central database. Currently there are 20 schools integrated into the system with another 48 to go, those 20 schools hold about half of our 46k student population.
The system allows (requires) student demographics to be entered through a web client, while grades, attendance, health, conduct, etc. are uploaded over night.
The system comes with the redo log file size set to 5k, which when the users in the 20 pilot schools get going causes a log switch about every 90 seconds. In my limited, steep learning curve expereince, this does not seem like a good thing. Add to that, they cancelled the Oracle Tuning class, which I have to wait until the system is in to take now.
So my questions (that the books don't really seem to want to answer):
How frequently should redo log file switches occur?
How large should my redo logs be?
I am guessing the answer to both of these questions is, It Depends. So my question really is, how do I determine what the correct settings for my installation are?
Tom
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Please see the official ORACLE-L FAQ: http://www.orafaq.com
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Author: Tom Schruefer
INET: tschruefer_at_mail.howard.k12.md.us
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists --------------------------------------------------------------------To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists --------------------------------------------------------------------To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Received on Mon Dec 31 2001 - 10:50:39 CST
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