| size of redolog? [message #123365] |
Sun, 12 June 2005 20:52  |
sunil_v_mishra
Messages: 506
Registered: March 2005
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Senior Member |
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hi,
I have 10 mb size of redolog files there are 3 redolog files . . .and nearly 20 log switch in 24 hour. . . now i want to make size of my redolog 75 MB each so that there can be only 2 log switch in 24 hour . . .
I just want to know if size of redolog file is change to 75 Mb does it going to effect perfornamce of database or any big issue can arise b'coz of this ?
Thank you
By:- Sunil
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| Re: size of redolog? [message #123417 is a reply to message #123365] |
Mon, 13 June 2005 06:51  |
limer
Messages: 15
Registered: June 2005
Location: Madrid
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Junior Member |
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Hello!
Experts say that you must change redolog each 20 minutes aprox. Then You have a well tuned redolog if you change once per hour. If you increase the redo files then you can decrease performance by 2 ways:
1- bigger files are slower
2- Copy bigger files to archivelog take more time.
could may help.
If works, don't touch it!
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| Re: size of redolog? [message #123496 is a reply to message #123365] |
Mon, 13 June 2005 14:20 |
sunil_v_mishra
Messages: 506
Registered: March 2005
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Senior Member |
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hi,
Smarti.........Actually i dont want my database in archive log mode as it take lot of space and i am going to take day to day backup of my database (i.e. after every 24 hr) so i will have backup and in case if crash occur then i can recover my database from redo log file as all required log will be present in it to recover the database. so full database recovery can possible.
Now if you have any suggestion or guidance to me in this matter then please let me know .. i will be thank full to you
One thing more limer Thanks for your reply...
From:- Sunil
[Updated on: Mon, 13 June 2005 14:23] Report message to a moderator |
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| Re: size of redolog? [message #123508 is a reply to message #123365] |
Mon, 13 June 2005 15:45 |
smartin
Messages: 1803
Registered: March 2005
Location: Jacksonville, Florida
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Senior Member |
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Jim: I'm sure I'm overlooking something similar, but I don't know how to follow your link above to find the good discussion on the subject? How do I find it, what am I missing?
Sunil:
"Actually i dont want my database in archive log mode as it take lot of space..."
Question 1:
If you have on one hand one large redo log file, of say 100 MB, and on the other hand you have 10 small redo log files, of say 10 MB each, how is either one of them different as far as space goes?
In other words, the space of your redo log data is determined by the amount of redo generated. Whether you put it all in one large file, or a bunch of small files, makes no difference as far as total space goes.
Question 2:
What happens if you have a day, a really busy day. Lots of modifications are made. Those modifications are very important. A very important day of high activity.
But because of so much redo generated on that busy day, oracle cycles back around and overwrites existing redo log files. You thought you had planned it so there would be enough and big enough redo files so that it would not cycle back, but because of the high activity in that special day it used more redo than you thought, causing it to cycle and overwrite earlier redo files.
Then, as luck would have it, that evenening, before you can take the backup, the server crashes, and you need to restore from backup. But all you can do is restore yesterday's copy, because some of the redo logs were overwritten, you can't recover all of that high activity, which was very important, that happened during the day. So now what do you do?
Statement 1:
If the data in your database is important to you, then stay in archivelog mode.
Statement 2:
Disk space is very cheap.
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| Re: size of redolog? [message #123511 is a reply to message #123365] |
Mon, 13 June 2005 15:54 |
DMcG
Messages: 51
Registered: May 2005
Location: Auckland, New Zealand
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Smartin gave you a classic example of what can happen when your DB is not in archive mode.
If you're seriously worried about the amount of disk space taken up by 200mb of log switches then try compressing your archived redo logs - they generally compress quite well.
Dougie McGibbon
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