Re: Buffer cache statistics (ratios) and CBO SQL optimization?

Geomancer wrote:
>
> > well they do until you saturate it (30 mins after boot :( ).
>
> If I have a 4-gig cacje on top of a 100 gig EMC array, then I only get
> 4% caching, right?
>
> I still find it hard to beleive that a logical I/O is only 10x-100x
> faster than a disk read.

Its easy enough to test...the hit ratio generator on my site is easily modified to do a timing test. The key thing is that an Oracle logical I/O is a lot more complex than a "read from memory".

JL has conjectured that you can get approx 10,000 LIO's per sec per 100Mhz of CPU.

hth
connor Received on Tue Dec 30 2003 - 04:37:05 CST