Mitchell,
A check point must occur at the interval, timeout, and log switch. Now in
my mind the least of these is the log switch which is controlled by the log file
size. Other than the checkpoint and it's associated overhead, the only thing
else that happens during a log switch is the archiver making a copy of the log
to the archive_dest.
Where does all of this lead, well the size of the log file in many ways
affects the granularity of the recovery that can later be accomplished if and
when a disk drive fails. I always assume that the worst thing possible will
happen, namely I'll loose an online redo log (and the active one to boot), when
that drive quits. Now if you've for a 100MB log file then there is 40MB or 30
minutes of transactions that are lost. On the other hand if you've got a 10MB
log with 3 minutes of transactions, then you can get a whole lot closer to right
now when you recover.
Which way you go is dependent on how close to failure time do you need to
get for your customenr (users) to be happy. In my case the least amount of lost
transactions resluts in the least amount of product that has to be
tossed/retested resulting in the least $.
Which way you decide to go is very much an individual choice. OH, BTW you
could mirror your log files to prevent the catastrophe, but in my case that
increases the disk $.
Dick Goulet
____________________Reply Separator____________________
Author: "Mitchell" <[EMAIL PROTECTED]>
Date: 4/30/2001 1:10 PM
Dear DBA
I have 130 gb database running on 7/24 basis. redo logfile size is 40mb and
oracle create about most to 400 archivive log. that mean log switch happend
at 3-4 min at peak time.
As oracle suggest, it is better log switch between 30min. (Why, if so that
need more recovery time?)
If I will increase the size to 100mb and make time around 30 min. How about
Log_checkpooint_interval. My currently setting is 2097152 (20mb).
log_checkpoint_timeout = 0
As my understand, the interval based on volume. If setting is 100mb, mean 5
check point will occured at 20mb interval. I am right?
Any suggest?
Mitchell
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