RE: Fav. Urban Legend... (Memory vs. Disk speeds)

    The memory vs. disk speed argument most likely stems from hardware access times. Memory is rated in nanoseconds (10E-9), and disk access times are in milliseconds (10E-6). Hence, memory is rated at 1000 times faster than disk (if these ratings are accurate...).

Alan

Alan Aschenbrenner
Oracle DBA
IHS Group

-----Original Message-----
Sent: Tuesday, March 19, 2002 9:29 AM
To: Multiple recipients of list ORACLE-L

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, 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
>
> taken.
>
> > Then you will have to go back to the _previous_ incarnation and redo the
> > restore and then perform a ccf/resetlogs (i.e. back to square one). If
> > you have a Cold backup, you restore the cold backup and go on with life.
> > I.e. in both cases (availability of cold or hot backup, lost online redo
> > log), you have lost transactions...
> >
> > Additionally, with a Hot backup and depending on what was lost, you can
> > at least perform tablespace/datafile recovery . With a cold backup, you
> > will have to restore the whole database....
> >
> > The point I was trying to make was that a Cold backup after a RESETLOGS
> > does not serve anything. Maybe there is still a gotcha I have not been
>
> able
>
> > to figure out, so Backup/restore Gurus: take a bash at this logic! I
> > would love to be corrected.
> >
> > (Btw, the previous recovery scenario was on 7.3.4 - things could have
> > changed since, and I have not been able to test that out...)
> >
> >
> > John Kanagaraj
> > Oracle Applications DBA
> > DBSoft Inc
> > (W): 408-970-7002
> >
> > Grace - Getting something we don't deserve
> > Mercy - NOT getting something we deserve
> >
> > Click on 'http://www.needhim.org' for Grace and Mercy that is freely
> > available!
> >
> > ** The opinions and statements above are entirely my own and not those
of
> > my employer or clients **

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