If anyone's after a nice high hit ratio, you can
download the source for procedure "choose_hit_ratio"
from my site...Some examples:
SQL> exec choose_a_hit_ratio(90);
Current ratio is: 86.24731
Another 79053 consistent gets needed...
Current ratio is: 90.5702
PL/SQL procedure successfully completed.
SQL> exec choose_a_hit_ratio(98,true);
Current ratio is: 90.5709
Another 1141299 consistent gets needed...
Magic for consultants like myself..
"You want a hit ratio of 98%... No problem"
:-)
- "Deshpande, Kirti" <kirti.deshpande_at_verizon.com>
wrote: > Not quite !! 99.999% or 'the five nines'
sounds much
> better ;-)
>
> With 64-bit computing we can address SGA sizes in
> the order of few TBs (if
> not PBs), why worry about disk I/Os except for two
> occasions ;-)) Then the
> 'five nines' can be 'nine nines'. Wow!! That sounds
> even better.. much much
> better ;-)))
>
>
> - Kirti
>
> -----Original Message-----
> Sent: Wednesday, March 20, 2002 5:48 AM
> To: Multiple recipients of list ORACLE-L
>
>
> Cary Milsap from hotsos has much data to confirm an
> approximate 1:100 ratio
> between LIO time and PIO time.
>
> Can we therefore conclude, that the buffer cache hit
> ratio should be 99%?
> :-)
>
> Rgds, Bjørn.
> On Wednesday 20 March 2002 10:48, Connor McDonald
> wrote:
> > Some rudimentary testing on a laptop here (500Mhz,
> > 512M RAM, typical single disk)
> >
> > a) visiting a single block via 4,000,000 logical
> IO's
> > got me approx 35000 gets/sec
> >
> > b) repeated full table scans similar system got me
> > approx 350 phys reads/sec
> >
> > After this extensive, thorough and exhaustive
> > exercise, I can definitely say that memory access
> > versus disk access (as it pertains to Oracle) is
> 100
> > times faster on this machine in single user mode
> >
> > I think we can generalise this to be the rule for
> all
> > servers under all conditions :-)
> >
> > Connor
> >
> >
> --
> Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> --
> Author: Deshpande, Kirti
> INET: kirti.deshpande_at_verizon.com
>
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Connor McDonald
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Received on Wed Mar 20 2002 - 15:14:40 CST
