Return-Path: Received: from newsfeed.cts.com (newsfeed.cts.com [209.68.248.164]) by naude.co.za (8.11.2/8.11.2) with SMTP id g2KDYMg19235 for ; Wed, 20 Mar 2002 08:34:22 -0500 Received: from fatcity.UUCP (uucp@localhost) by newsfeed.cts.com (8.9.3/8.9.3) with UUCP id FAA91769; Wed, 20 Mar 2002 05:34:35 -0800 (PST) Received: by fatcity.com (26-Feb-2001/v1.0g-b70/bab) via UUCP id 0042E3E5; Wed, 20 Mar 2002 04:48:21 -0800 Message-ID: Date: Wed, 20 Mar 2002 04:48:21 -0800 To: Multiple recipients of list ORACLE-L X-Comment: Oracle RDBMS Community Forum X-Sender: Mogens =?ISO-8859-1?Q?N=F8rgaard?= Sender: root@fatcity.com Reply-To: ORACLE-L@fatcity.com Errors-To: ML-ERRORS@fatcity.com From: Mogens =?ISO-8859-1?Q?N=F8rgaard?= Subject: Re: Fav. Urban Legend...Mem vs Disk Organization: Fat City Network Services, San Diego, California X-ListServer: v1.0g, build 70; ListGuru (c) 1996-2001 Bruce A. Bergman Precedence: bulk Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------020805040503070804040506" --------------020805040503070804040506 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by newsfeed.cts.com id FAA91769 I always thought 42 was a good number. Perhaps I was wrong. Bj=F8rn Engsig wrote: >Cary Milsap from hotsos has much data to confirm an approximate 1:100 ra= tio=20 >between LIO time and PIO time. =20 > >Can we therefore conclude, that the buffer cache hit ratio should be 99%= ? :-) > >Rgds, Bj=F8rn. >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 >> >> --- "Freeman, Robert " >>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@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, >>>>> >>>and backup of the control >>> >>>>>file from AFTER the same operation. I've done >>>>> >>>this about 3 times in >>> >>>>testing >>>> >>>>>and it works fine but it very very picky about >>>>> >>>the control file images. >>> >>>>>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: Friday, March 15, 2002 7:28 PM >>>>>To: Multiple recipients of list ORACLE-L >>>>> >>>>> >>>>>Hi Jared, >>>>> >>>>>>>* You *have* to take a COLD backup of the >>>>>>> >>>database after using >>> >>>>>>resetlogs. >>>>>> >>>>>>>(Not required - a Hot backup and archive >>>>>>> >>>logs is adequate. All hot >>> >>>>>>backups / >>>>>> >>>>>>>archive logs prior to that are invalid, >>>>>>> >>>though...) >>> >>>>>>Consider the following: >>>>>> >>>>>>Time: >>>>>> >>>>>>t0: database restored >>>>>>t1: database opened with RESETLOGS >>>>>>t2: hot backup started ( database in archive >>>>>> >>>log mode ) >>> >>>>>>t3: users input very important transactions >>>>>>t4: database crashes, and must be restored >>>>>> >>>>>>How will you recover the transactions from >>>>>> >>>time t3? >>> >>>>>As long as the online redologs are available, >>>>> >>>this should be no problem. >>> >>>>>I have successfully recovered databases where a >>>>> >>>log switch did not occur >>> >>>>>and recovery had to use an online redo log. (I >>>>> >>>am assuming that the lost >>> >>>>>datafiles will be restored from this hot backup >>>>> >>>fresh off the tapes) >>> >>>>>On the other hand, if the online redolog is >>>>> >>>hosed you have lost the >>> >>>>>transactions anyway, _regardless_ of the fact >>>>> >>>that a Cold backup was >>> >>=3D=3D=3D message truncated =3D=3D=3D >> >>=3D=3D=3D=3D=3D >>Connor McDonald >>http://www.oracledba.co.uk (mirrored at >>http://www.oradba.freeserve.co.uk) >> >>"Some days you're the pigeon, some days you're the statue" >> >>__________________________________________________ >>Do You Yahoo!? >>Everything you'll ever need on one web page >>from News and Sport to Email and Music Charts >>http://uk.my.yahoo.com >> > --------------020805040503070804040506 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit I always thought 42 was a good number. Perhaps I was wrong.

Bjørn Engsig wrote:
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

 --- "Freeman, Robert " <Robert_Freeman@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@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<
br>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,
and backup of the control

file from AFTER the same operation. I've done
this about 3 times in

testing

and it works fine but it very very picky about
the control file images.

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: Friday, March 15, 2002 7:28 PM
To: Multiple recipients of list ORACLE-L


Hi Jared,

* You *have* to take a COLD backup of the
database after using

resetlogs.

(Not required - a Hot backup and archive
logs is adequate. All hot

backups /

archive logs prior to that are invalid,
though...)

Consider the following:

Time:

t0: database restored
t1: database opened with RESETLOGS
t2: hot backup started ( database in archive
log mode )

t3: users input very important transactions
t4: database crashes, and must be restored

How will you recover the transactions from
time t3?

As long as the online redologs are available,
this should be no problem.

I have successfully recovered databases where a
log switch did not occur

and recovery had to use an online redo log. (I
am assuming that the lost

datafiles will be restored from this hot backup
fresh off the tapes)

On the other hand, if the online redolog is
hosed you have lost the

transactions anyway, _regardless_ of the fact
that a Cold backup was
=== message truncated ===

=====
Connor McDonald
http://www.oracledba.co.uk (mirrored at
http://www.oradba.freeserve.co.uk)

"Some days you're the pigeon, some days you're the statue"

__________________________________________________
Do You Yahoo!?
Everything you'll ever need on one web page
from News and Sport to Email and Music Charts
http://uk.my.yahoo.com


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