Re: How did you size you LOG_BUFFER ??

On 9 Apr 2004 04:57:15 -0700, Spendius <spendius_at_muchomail.com> wrote:

> Hi,
> Do you guys have some kind of rule to set this parameter ?
> In the 8i Designing & Tuning for Perf. book, ch. 20 they
> give a method to set this value up, with:
>> SELECT a.VALUE / DECODE(b.VALUE, 0, 1, b.VALUE)
>> FROM V$SYSSTAT a, V$SYSSTAT b
>> WHERE a.NAME = 'redo size' AND b.NAME = 'user commits';
>
> to get the avg # of redo records/commit which they recommend
> to multiply by the avg # of commits/second. I did this but
> it obviously led me to nonsensical figures (we already have
> log_buffer=163840 but this advice would've made us set it to
> about a value of 5000 !).
>
> Can anybody please give me some nice hint(s) ?
>
> Thanks.
> Spendius

Sounds daft, but it's actually quite sensible: Set it to 1MB and then forget about it.

If you later discover you are suffering from redo allocation retries or redo waits, then consider increasing it by a meg or two. But there's actually not much to worry about with the log buffer, because it gets flushed so frequently, it really doesn't need to be very big at all. 1MB is actually (usually) a little over-sized, but it won't do any harm.

Regards
HJR

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