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Home -> Community -> Mailing Lists -> Oracle-L -> Re: LOB columns and migrated rows
Thanks Mladen for your quick response.
The lob column table has just Pk and the lob column if I disable storage in row even then it will not stop rows from migrating if avg row len is 100k.
So far i have not used this feature (multi block size)that is why I am asking other people's suggestions/experiences before making the new database.
Thanks
From: Mladen Gogala <gogala@sbcglobal.net>
Reply-To: gogala@sbcglobal.net
To: chughhk@hotmail.com
CC: oracle-l@freelists.org
Subject: Re: LOB columns and migrated rows
Date: Thu, 02 Feb 2006 23:31:33 -0500
>
>On 02/02/2006 10:59:43 PM, hitender chugh wrote:
> > We have tables with LOB columns which are showing chained/migrated rows.
> > I want to know how to reduce the chaining/migration of rows for such tables?
>
>Disable storage in row.
>
>
> > Will putting these tables on tablespace with bigger blocksize say 32k will
> > help reducing migration and increase performance?
>
>It's the rows in the original blocks that are migrated or chained. The problem
>is that when you have a LOB column, not only descriptor is stored in row,
>up to 3500 bytes can be stored there as well.
>
> > Using multiple block size tablespace feature on 9i , the max blocksize is
> > 32k. If avg row len is more than 100k even placing LOB column tables on 32k
> > blocksize will not help.
>
>Do you find it to be any faster? You will have to allocate a separate cache
>for 32k blocks which can not be used for anything else and will normally
>be underutilized.
>
> > What are the performance implications of having tables spread out on
> > different blocksize tablespace?
>
>Don't tell me that you actually created a database with multiple block sizes
>without testing it first?
>
>
> > I have not used this feature before so I want to know what is the
> > experience/suggestions of other people on this.
>
>Multiple block sizes are normally used to plug in tablespaces from another database,
>typically from an OLTP to DW. It's much faster then export and import. Multiple
>block sizes are practically useless for anything else.
>--
>Mladen Gogala
>http://www.mgogala.com
>
>--
>http://www.freelists.org/webpage/oracle-l
>
>
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