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db_32k_cache_size RHEL [message #684358]

Tue, 18 May 2021 13:41

burkinaone
Messages: 11
Registered: October 2020

Junior Member

Hello.
Source DB is 11.2.0.4 on AIX 7.1
Destination is Oracle 19.3 on RHEL 7.9

I have a 32k block size tablespace in the source.
I want to create the same tablespace on the destination.
Of course I need to set db_32k_cache_size first (to 64M).

Is it possible and advisable to do so on RHEL?
Thanks for your replies.

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Re: db_32k_cache_size RHEL [message #684359 is a reply to message #684358]

Tue, 18 May 2021 14:29

Michel Cadot
Messages: 68785
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

This parameter does not care about the OS.

It seems your question is somewhat of an XY problem one.

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Re: db_32k_cache_size RHEL [message #684360 is a reply to message #684359]

Tue, 18 May 2021 15:48

burkinaone
Messages: 11
Registered: October 2020

Junior Member

Why do you say this parameter does not care about OS?
Read this: https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/DB_nK_CACHE_SIZE.html#GUID-025ECEB2-E535-49D2-9721-268E3925FE09

and this (slide 6): http://www.nyoug.org/Presentations/2004/200409mblk.pdf

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Re: db_32k_cache_size RHEL [message #684361 is a reply to message #684360]

Tue, 18 May 2021 16:59

EdStevens
Messages: 1377
Registered: September 2013

Senior Member

Well, it is true that you cannot set the cache size to a value that the OS does not support, so to that degree it does care about the OS. But beyond that what are you expecting? Your question seemed to imply that you are expecting a given size that is supported by the OS to perhaps not be recommended.

Actually, there have been a lot of studies (I don't have the references handy) that indicate the the oracle default 8k cache size works quite well for the vast majority of applications. Only in highly specialized (dare I say contrived?) cases does it appear worthwhile to muck around with other sizes.

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Re: db_32k_cache_size RHEL [message #684363 is a reply to message #684360]

Tue, 18 May 2021 23:47

Michel Cadot
Messages: 68785
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

burkinaone wrote on Tue, 18 May 2021 22:48

Why do you say this parameter does not care about OS?
Read this: https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/DB_nK_CACHE_SIZE.html#GUID-025ECEB2-E535-49D2-9721-268E3925FE09

and this (slide 6): http://www.nyoug.org/Presentations/2004/200409mblk.pdf

Ah ah! What is the purpose of your question then?
You want to "set db_32k_cache_size first" but it is not allowed, so to answer "Is it possible and advisable to do so?", the answer is obviously "no". Razz

(Note that your slide is 17 years old and maybe not accurate.)

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Re: db_32k_cache_size RHEL [message #684371 is a reply to message #684363]

Fri, 21 May 2021 14:45

burkinaone
Messages: 11
Registered: October 2020

Junior Member

Monsieur Cadot, leave the discussion to the DBAs

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Re: db_32k_cache_size RHEL [message #684372 is a reply to message #684371]

Fri, 21 May 2021 15:27

EdStevens
Messages: 1377
Registered: September 2013

Senior Member

burkinaone wrote on Fri, 21 May 2021 14:45

Monsieur Cadot, leave the discussion to the DBAs

I have just retired after a 40-year career in IT (from before when it was called "IT") with the last 25 or so years of it as an Oracle DBA. I have been a very active participant of this forum for over 7 years. I will vouch for Monsieur Cadot as one of the most respected DBAs here.

So what's your beef?

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