From oracle-l-bounce@freelists.org Mon Jun 6 13:28:53 2005 Return-Path: Received: from air891.startdedicated.com (root@localhost) by orafaq.com (8.12.10/8.12.10) with ESMTP id j56ISrA3029708 for ; Mon, 6 Jun 2005 13:28:53 -0500 X-ClientAddr: 206.53.239.180 Received: from turing.freelists.org (freelists-180.iquest.net [206.53.239.180]) by air891.startdedicated.com (8.12.10/8.12.10) with ESMTP id j56ISpNi029688 for ; Mon, 6 Jun 2005 13:28:51 -0500 Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 9D58A1BBDA8; Mon, 6 Jun 2005 12:25:41 -0500 (EST) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 25433-05; Mon, 6 Jun 2005 12:25:41 -0500 (EST) Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 1C6681BBCAE; Mon, 6 Jun 2005 12:25:41 -0500 (EST) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Mvt/2yE0yJAxOHGMPU6kE7lHUyDveoqthpgo9IIRUYk0jxWQlHnGs++frrLlsbUn+w7heedFGKnMecVjTqH+xxFyXGjIWLnbN178BMrJ+g6gviY4R2UAFQWV7eA6PxIuYUaf+MEgXhazuMLBRnHYzxg9s1d2gW5H7Ni37sdJPzQ= Message-ID: <52a152eb05060610233e353a0@mail.gmail.com> Date: Mon, 6 Jun 2005 13:23:19 -0400 From: Christo Kutrovsky To: Jared Still Subject: Re: "cache buffer chains" misses > 0 and spins & sleep[1-4] are zero, yet sleeps > 0 Cc: oracle-l In-Reply-To: Mime-Version: 1.0 Content-type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Content-Disposition: inline References: <52a152eb050604110177e32e98@mail.gmail.com> X-archive-position: 20703 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: kutrovsky.oracle@gmail.com Precedence: normal Reply-To: kutrovsky.oracle@gmail.com X-list: oracle-l X-Virus-Scanned: by amavisd-new-20030616-p9 (Debian) at avenirtech.net X-Spam-Level: X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on air891.startdedicated.com X-Spam-Status: No, hits=0.0 required=5.0 tests=AWL autolearn=ham version=2.63 A little bit of both. This snapshot was during "offload" period, during the problematic period i = have: Latch Name Requests Misses Sleeps Sleeps 1-= >4 -------------------------- -------------- ----------- ----------- ---------= --- cache buffers chains 245,864,551 171,099 89,853 0/0/0/0/0 cache buffers lru chain 8,827,850 102,355 4,694 97708/460= 1/4 5/1/0 library cache 8,081,449 88,918 8,436 80625/815= 6/1 31/6/0 shared pool 2,383,770 22,134 456 21691/430= /13 /0/0 We know what the problem is, the academic question is why the zeros in spins and sleep[1-4]. I did not post the problematic snapshot as i wanted to concentrate on the fact that the spin & sleeps is all zeroes. On 6/6/05, Jared Still wrote: > Hi Chris, >=20 > For the short answer, see > http://www.ixora.com.au/q+a/latches.htm. >=20 > Oracle spins then sleeps if the spin did not obtain a latch. >=20 > With a request:miss ratio of 15249:1 and 133 spins that successfully > obtained the latch, I am wondering if this is considered a performance > problem, or an academic exercise? >=20 >=20 > --=20 > Jared Still > Certifiable Oracle DBA and Part Time Perl Evangelist >=20 >=20 > On 6/4/05, Christo Kutrovsky wrote: > > Hello all, > >=20 > > Latch Sleep breakdown for DB: WEBP1 Instance: webp1 Snaps: 32412 -324= 13 > > -> ordered by misses desc > >=20 > > Get =20 > Spin & > > Latch Name Requests Misses =20 > Sleeps Sleeps 1-=3D > > >4 > > -------------------------- -------------- ----------- ----------- > ---------=3D > > --- > > ... > > cache buffers chains 30,194,375 1,980 133 > 0/0/0/0/0 > > ... > >=20 > > I am looking at this statspack extract over 20 minutes. I have a very > > specific question. > >=20 > > Given that I have ~2000 misses and 133 sleeps, howcome I dont have > > anything in spins and sleeps[1-4] ?=20 > >=20 > > Are the cache buffer chains special, i.e. there is no spinning to > > acquire them ? And if there are sleeps, last column is supposed to be > > 4 or more, yet it is still zero? > >=20 > > Looking in v$latch: > >=20 > > ADDR=3D095000D3E0=20 > > LATCH#=3D0998 > > LEVEL#=3D091 > > NAME=3D09cache buffers chains > > GETS=3D09113996341015 > > MISSES=3D09286248205 > > SLEEPS=3D092787346 > > IMMEDIATE_GETS=3D093233325716 > > IMMEDIATE_MISSES=3D0912384650 > > WAITERS_WOKEN=3D090 > > WAITS_HOLDING_LATCH=3D092933754=20 > > SPIN_GETS=3D090 > > SLEEP1=3D090 > > SLEEP2=3D090 > > SLEEP3=3D090 > > SLEEP4=3D090 > > SLEEP5=3D090 > > SLEEP6=3D090 > > SLEEP7=3D090 > > SLEEP8=3D090 > > SLEEP9=3D090 > > SLEEP10=3D090 > > SLEEP11=3D090 > > WAIT_TIME=3D090 > >=20 > >=20 > > You can see there's a large number of gets/misses but NONE in=20 > > spin_gets and sleeps 1-4, why is that ? > >=20 > >=20 > >=20 >=20 --=20 Christo Kutrovsky Database/System Administrator The Pythian Group -- http://www.freelists.org/webpage/oracle-l