Re: One control file/redo member with ASM ok?

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.

-- 
Thomas Kyte
Oracle Public Sector
http://asktom.oracle.com/
opinions are my own and may not reflect those of Oracle Corporation