Thomas Kyte wrote:
> In article <41eb1e18$1_1_at_127.0.0.1>, DA Morgan says...
>
>>Thomas Kyte wrote:
>>
>>
>>>In article <beolu01umcqbaft3pmdmu5isst1c4as0bg_at_4ax.com>, Sybrand Bakker says...
>>>
>>>
>>>>On 16 Jan 2005 10:25:25 -0800, domenicg_at_hotmail.com (Domenic) wrote:
>>>>
>>>>
>>>>
>>>>>Is it acceptable to use one control file and one redo log member only
>>>>>(per group) on a database using ASM, where ASM is doing the mirroring?
>>>>>What's Oracle's recommendation/opinion on this? Wouldn't two control
>>>>>files and two redo members per group be overkill when ASM is doing the
>>>>>mirroring also?
>>>>>
>>>>>Domenic.
>>>>
>>>>Oracle requires 2 control files. It won't start without 2 control
>>>>files.
>>>>Mirroring only protects you against hardware failure.
>>>>It doesn't protect you against someone inadvertently deleting a
>>>>controlfile.
>>>>Also the controlfile is usually only a few Mb's big. It would be very
>>>>strange to try to save a few Mb's and instead increase the risk
>>>>someone blows up your database.
>>>>
>>>>
>>>>--
>>>>Sybrand Bakker, Senior Oracle DBA
>>>
>>>
>>>Really?
>>>
>>>SQL> startup pfile=initora9ir2.ora
>>>ORACLE instance started.
>>>
>>>Total System Global Area 269554828 bytes
>>>Fixed Size 451724 bytes
>>>Variable Size 201326592 bytes
>>>Database Buffers 67108864 bytes
>>>Redo Buffers 667648 bytes
>>>Database mounted.
>>>Database opened.
>>>SQL> show parameter control
>>>
>>>NAME TYPE VALUE
>>>------------------------------------ ----------- ------------------------------
>>>control_file_record_keep_time integer 7
>>>control_files string /home/ora9ir2/oradata/ora9ir2/
>>> control01.ctl
>>>SQL>
>>>
>>>
>>>(they have the control files mirrored via ASM mirroring)
>>
>>I have mixed feelings on this one.
>>
>>While technically you are correct ... advising someone that they can do
>>this invites a very dangerous behaviour. Companies may suffer greviously
>>because someone reads this as Tom Kyte saying it is ok. And even I would
>>gleefully do what you recommend or what I assume you have sanctioned.
>
>
> I didn't say "do this", I just said "it is not true that you need two -- and you
> do understand that ASM has made it so that there are two transparently"
>
> ASM mirrors or triple mirrors. There is redundancy there already.
>
> Oracle does not require two control files.
> Oracle does suggest that the minimum should be two.
I understood but only because I have read the doc. And while I have
never personally had a corrupted control file under ASM it still gives
me the shakes.
See you in Victoria.
--
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)
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Received on Mon Jan 17 2005 - 16:23:10 CST
