I think you may have missed my sarcasm - I've been on
the anti-cache hit ratio bandwagon for a long time...
Cheers
Connor
- DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM> wrote:
> Connor - Cary Millsap presented the results of 10
> trace files in a Hotsos
> seminar I attended. The ratio ranged from a high of
> 108.57 down to a low of
> 0.79. The point is that the ratio is nowhere near
> the oft-quoted 10,000.
> This means that logical I/Os are not insignificant.
> Even if physical I/O
> were eliminated (all blocks cached, 100% cache hit
> ratio), response time
> would not drop to zero. This is why the emphasis in
> tuning is shifting from
> simple ratios to examining wait times. If the most
> significant wait time is
> physical I/O, then changing that will improve
> overall performance. But if
> the most significant wait time lies in another area,
> then you may make
> significant improvements in physical I/O and still
> not improve overall
> performance. I certainly wouldn't claim to be an
> Oracle tuning expert, but I
> believe that the new ideas on tuning that are
> emerging provide a significant
> step forward in making Oracle tuning more of a
> logical process than a
> collection of rules of thumb.
> Dennis Williams
> DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
>
> -----Original Message-----
> Sent: Wednesday, March 20, 2002 3:49 AM
> To: Multiple recipients of list ORACLE-L
>
>
> 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
>
> --- "Freeman, Robert " <Robert_Freeman_at_csx.com>
> wrote: > I've heard the disk vs. memory arguments
> before, but
> > never have seen
> > quantifiable data either way... if anyone has any,
> > I'd love to see it.
> >
> > RF
> >
> > Robert G. Freeman - Oracle8i OCP
> > Oracle DBA Technical Lead
> > CSX Midtier Database Administration
> >
> > The Cigarette Smoking Man: Anyone who can appease
> a
> > man's conscience can
> > take his freedom away from him.
> >
> >
> >
> > -----Original Message-----
> > Sent: Monday, March 18, 2002 5:54 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Robert - So THAT is the title of your next book.
> I'm
> > primed to buy it
> > already.
> > I just recalled a legend, maybe. "Disk is 10,000
> > times slower than memory,
> > so memory access times are infinitesimal compared
> to
> > disk access". Cary
> > Millsap covers this in his Hotsos Clinic. He has
> run
> > tests that prove "ain't
> > so". The point is that you can't just use ratios
> to
> > tune Oracle, but need to
> > look at wait times.
> > Dennis Williams
> > DBA
> > Lifetouch, Inc.
> > dwilliams_at_lifetouch.com
> >
> >
> > -----Original Message-----
> > Sent: Monday, March 18, 2002 1:04 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > So, does the CoO (Church of Oracle) have an
> > infallibility doctrine then???
> >
> > ... From the Book of Oracle, chapter 5 ...
> >
> > ...and the DBA did look upon his database, and he
> > saw it was good.
> > His tablespace datafiles being distributed tither
> > and fro, spread amongst
> > the
> > platters of his disks. And he did complete that
> > which was called
> > documentation,
> > and then he rested from his labors, and drank
> > Mountain Dew Code Red...
> >
> >
> > :-)
> >
> > Robert G. Freeman - Oracle8i OCP
> > Oracle DBA Technical Lead
> > CSX Midtier Database Administration
> >
> > The Cigarette Smoking Man: Anyone who can appease
> a
> > man's conscience can
> > take his freedom away from him.
> >
> >
> >
> > -----Original Message-----
> > Sent: Monday, March 18, 2002 12:25 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> >
> > Hey, you're an author!
> >
> > I expect perfection, grace and infallibility. ;)
> >
> > Jared
> >
> > On Monday 18 March 2002 07:33, Freeman, Robert
> > wrote:
> > > And hey, it was Sunday morning at 0700
> > something... what do you
> > > expect from me anyways??? :-)))))))
> > >
> > > RF
> > >
> > > Robert G. Freeman - Oracle8i OCP
> > > Oracle DBA Technical Lead
> > > CSX Midtier Database Administration
> > >
> > > The Cigarette Smoking Man: Anyone who can
> appease
> > a man's conscience can
> > > take his freedom away from him.
> > >
> > >
> > >
> > > -----Original Message-----
> > > Sent: Sunday, March 17, 2002 6:43 PM
> > > To: Multiple recipients of list ORACLE-L
> > >
> > > On Sunday 17 March 2002 07:53, Freeman, Robert
> > wrote:
> > > > 1. You do not open the database to users until
> > AFTER you do a backup
> > (hot
> > > > or cold, dosen't mater) at point t2.
> > >
> > > Well, yeah, that was the point. It doesn't have
> > to be a cold backup, but
> > > since you can't do any work, it may as well be a
> > cold backup.
> > >
> > > Jared
> > >
> > > > 2. There is a method of recovering a database
> > (8i +) after RESETLOGS has
> > > > been
> > > > issued with archived redo logs. I discussed it
> > in my DBA World Tour
> > > > backup and
> > > > recovery presentation. To do this, you MUST
> have
> > the control file for
> > the
> > > > database from BEFORE the resetlogs operation,
>
=== message truncated ===
Connor McDonald
http://www.oracledba.co.uk (mirrored at
http://www.oradba.freeserve.co.uk)
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Received on Wed Mar 20 2002 - 15:14:36 CST
