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, Bj�rn. 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 " <[EMAIL PROTECTED]> > 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. > > [EMAIL PROTECTED] > > > > > > -----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 > > === 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 -- Bj�rn Engsig, Miracle A/S http://MiracleAS.dk -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: =?iso-8859-1?q?Bj=F8rn=20Engsig?= INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). 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