RE: How to set SGA size initially?

From: Gaja Krishna Vaidyanatha <gajav_at_yahoo.com>
Date: Thu, 22 Jun 2000 19:03:43 -0700 (PDT)
Message-Id: <10536.110213@fatcity.com>

Gopal,

My original posting communicates exactly your point, i.e. "The size of the redo log buffer should be around 512K". There are some exceptional cases where I have had the need to set it at 1M (due to very heavy transactional volume - 1000s of transactions) and that is what I wrote (exception).

I am not sure what issue you are alluding to with regards to "commit confirmation delay" and the 1M redo log buffer size that we are referring to here. I am not aware of such an issue, so if you care to explain, it will be greatly beneficial for everyone.

I do agree that with a 1M redo log buffer, it takes longer for the 33%-write threshold to occur - the write is done after 333K worth of redo entries instead of 166.5K worth of redo entries with a redo log buffer sized at 512K. No arguments there.

So effectively, both of us have said the same thing and I am wondering where the disconnect is. May be I am missing something???? Here is the snippet from my original posting:

>Further, the default size of the redo log buffer is
>(4*db_block_size), and that is definitely too small. For most
>environments the size of the redo log buffer varies from about
>256K - 1M, where the average size is at 512K and 1M being the
>exception and not the rule.

Cheers,

Gaja.

• kgopalakrishnan <kgopalakrishnan_at_mantraonline.com> wrote:> > Gaja / Vikas !
  > > I agree with Gaja except for the log buffer size.
  > Bigger buffer(s) size is/are always NOT better> (atleast in)
  LOG_BUFFERS.>
  > The ideal size for log buffer will be 3-4 times of
  > your average redo size (redo bytes/ redo writes).>
  > And increasing log buffers beyond 512 k will not yield
  > any significant benefit and will be wasted (lgwr will start
  > writing to log files once the buffer is 33% full.. right?)
  > and some times it MAY increase the commit confirmation delay.>
  > YMMV>
  > K Gopalakrishnan> Bangalore, INDIA>
  http://www.geocities.com/kgkrish>

> stuff deleted<

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Gaja Krishna Vaidyanatha | gajav_at_yahoo.com Brio Technology | (972)-304-1170

"Opinions and views expressed are my own and not of Brio Technology"

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