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Home -> Community -> Mailing Lists -> Oracle-L -> 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_at_competitrack.com 212-604-0200 x106 On 8/7/2002 11:54 AM, Fink, Dan <Dan.Fink_at_mdx.com> wrote:Received on Wed Aug 07 2002 - 11:49:30 CDT
>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_at_tufts.edu
>>
>> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
>> San Diego, California -- Public Internet access / Mailing
>Lists
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>> --
>> Please see the official ORACLE-L FAQ: http://www.orafaq.com
>> --
>> Author: Fink, Dan
>> INET: Dan.Fink_at_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
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>--
>Please see the official ORACLE-L FAQ: http://www.orafaq.com
>--
>Author: Joe Armstrong-Champ
> INET: joseph.armstrong-champ_at_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_at_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_at_mdx.com
>
>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
>San Diego, California -- Public Internet access / Mailing
>Lists
>--------------------------------------------------------------------
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>(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_at_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_at_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).
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