RE: Anyone using multi-block sizes for their databases

From: Murching, Bob <bob_murching_at_BUDCO.com>
Date: Thu, 21 Jul 2005 14:33:31 -0400
Message-ID: <FDE18F41BE19D611A5AE00306E110E0F0F4E7EDF@budco_exch1.budco.com>

I more or less agree with the below sentiment. We moved to multiple block sizes pretty aggressively out of the gate with 10g, then quickly ended up cutting our losses and going back to an database-wide standard. It was mostly a manageability issue - with multiple block sizes, now we had one more thing to worry about: tuning the different buffer cache pools. Once you take a few moments to look at the capability and its primary weakness, you quickly realize that it's only a matter of time before Oracle auto-allocates RAM to the different buffer cache pools. I think we'll be taking advantage of multiple block sizes if and when that functionality becomes available. Until then, "just pick 8k or 16k, then go back to tuning the SQL and building the right data model" remains the most effective mechanism for tuning....

-----Original Message-----

From: Lex de Haan [mailto:lex.de.haan_at_naturaljoin.nl] Sent: Thursday, July 21, 2005 12:52 PM
To: juancarlosreyesp_at_gmail.com; Oracle-L_at_freelists.org Subject: RE: Anyone using multi-block sizes for their databases

Juan,

with all due respect, I believe this is *not* a good advice. I actually think it is a *bad* advice. you try to achieve something with the wrong technique, at a way too high price.

let me first say that the only *intended* reason for multiple blocksizes is to make transportable tablespaces more flexible. any other reason might have its merits, but should be considered with caution.

the biggest disadvantage of a segmented cache is that free space gets segmented too, obviously -- typically leading to much more memory wastage than with a single unsegmented buffer cache.

kind regards,

Lex.  

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-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Juan Carlos Reyes Pacheco
Sent: Thursday, July 21, 2005 18:45
To: Oracle-L_at_freelists.org
Subject: Re: Anyone using multi-block sizes for their databases

Hi,
This works really nice, this allows to create separate areas of memory for different things.
For example big blobs documents, in a 32k normal tables 8k indexes 16k, etc. etc.

You have to set the database memory cache in the init.ora for each different block size.
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http://www.freelists.org/webpage/oracle-l Received on Thu Jul 21 2005 - 13:35:53 CDT