From oracle-l-bounce@freelists.org Mon Jun 6 13:16:26 2005 Return-Path: Received: from air891.startdedicated.com (root@localhost) by orafaq.com (8.12.10/8.12.10) with ESMTP id j56IGQYf026649 for ; Mon, 6 Jun 2005 13:16:26 -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 j56IGQNi026643 for ; Mon, 6 Jun 2005 13:16:26 -0500 Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id BB3EC1BBCF1; Mon, 6 Jun 2005 12:13:16 -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 23319-04; Mon, 6 Jun 2005 12:13:16 -0500 (EST) Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 44B0E1BBD6A; Mon, 6 Jun 2005 12:13:16 -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:references; b=PZ2Jo7veXG+9BmSoR5Zor0YW0j/sezJ3I+OP6WERII/2/tI7AzrNLZKw/Z6diCVpicl4eGorZVAZVQKpCQAwjNsrSheAzoHajIXyW2SJ/4b9DJyATpJX5uy7hP1GlH95u7Nn1M1imi0tYKMoVZLaW2j3BwYfdI+IR/DTkaYZLTc= Message-ID: Date: Mon, 6 Jun 2005 10:11:23 -0700 From: Jared Still To: kutrovsky.oracle@gmail.com Subject: Re: "cache buffer chains" misses > 0 and spins & sleep[1-4] are zero, yet sleeps > 0 Cc: oracle-l In-Reply-To: <52a152eb050604110177e32e98@mail.gmail.com> Mime-Version: 1.0 Content-type: text/plain References: <52a152eb050604110177e32e98@mail.gmail.com> Content-Transfer-Encoding: 8bit X-archive-position: 20697 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: jkstill@gmail.com Precedence: normal Reply-To: jkstill@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 Hi Chris, For the short answer, see http://www.ixora.com.au/q+a/latches.htm. Oracle spins then sleeps if the spin did not obtain a latch. 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? -- Jared Still Certifiable Oracle DBA and Part Time Perl Evangelist On 6/4/05, Christo Kutrovsky wrote: > > Hello all, > > Latch Sleep breakdown for DB: WEBP1 Instance: webp1 Snaps: 32412 -32413 > -> ordered by misses desc > > Get Spin & > Latch Name Requests Misses Sleeps Sleeps 1-= > >4 > -------------------------- -------------- ----------- ----------- > ---------= > --- > ... > cache buffers chains 30,194,375 1,980 133 0/0/0/0/0 > ... > > I am looking at this statspack extract over 20 minutes. I have a very > specific question. > > Given that I have ~2000 misses and 133 sleeps, howcome I dont have > anything in spins and sleeps[1-4] ? > > 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? > > Looking in v$latch: > > ADDR=095000D3E0 > LATCH#=0998 > LEVEL#=091 > NAME=09cache buffers chains > GETS=09113996341015 > MISSES=09286248205 > SLEEPS=092787346 > IMMEDIATE_GETS=093233325716 > IMMEDIATE_MISSES=0912384650 > WAITERS_WOKEN=090 > WAITS_HOLDING_LATCH=092933754 > SPIN_GETS=090 > SLEEP1=090 > SLEEP2=090 > SLEEP3=090 > SLEEP4=090 > SLEEP5=090 > SLEEP6=090 > SLEEP7=090 > SLEEP8=090 > SLEEP9=090 > SLEEP10=090 > SLEEP11=090 > WAIT_TIME=090 > > > You can see there's a large number of gets/misses but NONE in > spin_gets and sleeps 1-4, why is that ? > > > -- http://www.freelists.org/webpage/oracle-l