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 g78DQQ310313 for ; Thu, 8 Aug 2002 09:26:26 -0400 Received: from fatcity.UUCP (uucp@localhost) by newsfeed.cts.com (8.9.3/8.9.3) with UUCP id GAA01917; Thu, 8 Aug 2002 06:26:17 -0700 (PDT) Received: by fatcity.com (26-Feb-2001/v1.0g-b71/bab) via UUCP id 004AEE26; Thu, 08 Aug 2002 06:18:21 -0800 Message-ID: Date: Thu, 08 Aug 2002 06:18:21 -0800 To: Multiple recipients of list ORACLE-L X-Comment: Oracle RDBMS Community Forum X-Sender: Alan Davey Sender: root@fatcity.com Reply-To: ORACLE-L@fatcity.com Errors-To: ML-ERRORS@fatcity.com From: Alan Davey Subject: Re: duplexing redos and archives Organization: Fat City Network Services, San Diego, California X-ListServer: v1.0g, build 71; ListGuru (c) 1996-2001 Bruce A. Bergman Precedence: bulk Mime-Version: 1.0 Content-Type: text/plain; charset="US-Ascii" Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by naude.co.za id g78DQQ310313 Thanks. -- Alan Davey adavey@competitrack.com 212-604-0200 x106 On 8/7/2002 6:16 PM, Gogala, Mladen wrote: >I believe that oracle sets the status of the particular member in > >v$logfile table to 'UNUSABLE' and that it archives only the usable > >member. Cary has mentioned that LGWR does actually read the file >to >ensure consistency, so I don't believe that a corrupt file will be > >archived. > >Mladen Gogala >Oracle DBA >Phone: (203) 459-6855 >Email: mgogala@oxhp.com > > > >> -----Original Message----- >> From: Alan Davey [mailto:adavey@competitrack.com] >> Sent: Wednesday, August 07, 2002 12:50 PM >> To: Multiple recipients of list ORACLE-L >> Subject: Re: duplexing redos and archives >> >> >> Dan, >> >> So in your scenario, what happens when Oracle goes to archive >> the redo logs? Does it first compare the duplexed versions, >> or does it just archive the first (corrupted) file in the group? >> >> Regards, >> -- >> >> Alan Davey >> adavey@competitrack.com >> 212-604-0200 x106 >> >> >> On 8/7/2002 11:54 AM, Fink, Dan wrote: >> >Joe, >> > #2 could result from the processes/hardware path >> outside of Oracle's >> >control. For example, the redo logs are written to disks >> with separate >> >caches. Disk #1 cache soft corrupts the data being stored, but >it >> >is not >> >caught by the system. Disk#2 cache writes it correctly. The key >is >> >that >> >Oracle 'thinks' the log has been written correctly when it was >not. >> >I'm not >> >a hardware/systems expert, but the scenario of one file >> being corrupted >> >where another is not sounds possible, but unlikely. Then again...why > >> >take >> >the chance. >> > >> > >> >-----Original Message----- >> >Sent: Wednesday, August 07, 2002 6:53 AM >> >To: Multiple recipients of list ORACLE-L >> > >> > >> >Dan, >> > >> >If scenario #2 happened wouldn't both sets of logs be corrupted >since >> >oracle is writing the same thing to both files? >> > >> >BTW, from the tone of everyone responding I think I'll push for >> >continuing to duplex. Thanks. >> > >> >Joe >> > >> >"Fink, Dan" wrote: >> >> >> >> This may be 'old school' thinking, but I prefer to duplex my >redo >> >logs. >> >Why? >> >> Because there are some things that mirroring cannot protect >you >> >against. >> >> 1. The deletion of a redo log through human error (been there, > >> >recovered >> >> from it...) >> >> 2. The logical corruption of a redo log (never experienced >> it myself, >> >but >> >it >> >> is theortically possible) >> >> 3. Oracle's fault tolerance regarding the ability to function >as >> >long as 1 >> >> redo log in a group is accessible >> >> >> >> Considering the critical nature of the redo logs (lose one and > >> >your >> >recovery >> >> is done...and perhaps your job) and their small size in relation > >> >to >> >overall >> >> databse size, duplexing in a group makes sense. >> >> >> >> This is one of those issues where valid arguements exist on >both >> >sides. In >> >> some ways, the logical arguements are on the side of not duplexing > >> >redo >> >logs >> >> that are mirrored. However, when you consider that the loss >or >> >corruption >> >of >> >> a single redo log can cause the database to be unrecoverable >is >> >enough to >> >> justify the cost of duplexing. >> >> >> >> Just my humble (old school) opinion >> >> >> >> Dan Fink >> >> >> >> -----Original Message----- >> >> Sent: Tuesday, August 06, 2002 12:13 PM >> >> To: Multiple recipients of list ORACLE-L >> >> >> >> Currently we are duplexing our redo logs and archive logs through >> >> oracle. We do this at the oracle level because we are >> using mirroring >> >> (raid0?) and if we lose a redo log or archive file the database > >> >will not >> >> be affected. >> >> >> >> We will be moving to raid5 arrays in the future and are wondering >> >> whether we still need to do the duplexing. Since the arrays >are >> >made up >> >> of data disks plus a parity disk plus a hot swap do we need >to >> >worry >> >> about losing a redo log? Our sys admins are telling us we don't > >> >and I >> >> tend to agree with them but we want to get other opinions on >the >> >> subject. >> >> >> >> How are shops handling this who are using raid5? >> >> >> >> Thanks. >> >> Joe >> >> -- >> >> Please see the official ORACLE-L FAQ: http://www.orafaq.com >> >> -- >> >> Author: Joe Armstrong-Champ >> >> INET: Joseph.Armstrong-Champ@tufts.edu >> >> >> >> 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: ListGuru@fatcity.com (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). >You >> >may >> >> also send the HELP command for other information (like >> subscribing). >> >> -- >> >> Please see the official ORACLE-L FAQ: http://www.orafaq.com >> >> -- >> >> Author: Fink, Dan >> >> INET: Dan.Fink@mdx.com >> >> >> >> 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: ListGuru@fatcity.com (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). >You >> >may >> >> also send the HELP command for other information (like >> subscribing). >> >-- >> >Please see the official ORACLE-L FAQ: http://www.orafaq.com >> >-- >> >Author: Joe Armstrong-Champ >> > INET: joseph.armstrong-champ@tufts.edu >> > >> >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: ListGuru@fatcity.com (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). You >may >> >also send the HELP command for other information (like subscribing). >> >-- >> >Please see the official ORACLE-L FAQ: http://www.orafaq.com >> >-- >> >Author: Fink, Dan >> > INET: Dan.Fink@mdx.com >> > >> >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: ListGuru@fatcity.com (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). You >may >> >also send the HELP command for other information (like subscribing). >> > >> > >> >> -- >> Please see the official ORACLE-L FAQ: http://www.orafaq.com >> -- >> Author: Alan Davey >> INET: adavey@competitrack.com >> >> 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: ListGuru@fatcity.com (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). You >may >> also send the HELP command for other information (like subscribing). >> >-- >Please see the official ORACLE-L FAQ: http://www.orafaq.com >-- >Author: Gogala, Mladen > INET: MGogala@oxhp.com > >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: ListGuru@fatcity.com (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). You may >also send the HELP command for other information (like subscribing). > > -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Alan Davey INET: adavey@competitrack.com 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: ListGuru@fatcity.com (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). You may also send the HELP command for other information (like subscribing).