Re: Chained Rows and DB_BLOCK_SIZE - any relationship ???

A copy of this was sent to "Kevin A Lewis" <KevinALewis_at_Hotmail.com> (if that email address didn't require changing) On Fri, 13 Aug 1999 11:34:44 +0100, you wrote:

>Is there a relationship between DB_BLOCK_SIZE and chained rows. I thought
>the controlling factors were the table PCTFREE and PCTUSED settings and the
>use of column types such as VARCHAR2.
>
>My limited understanding of the mathematics suggests to me that there could
>be a relationship. I have seen one or two people on this type of forum
>suggest a link. However I was wondering if anyone else had any practical or
>experimental experience to draw on.
>
>Regards

sure it does.

Lets say you have a table:

create table foo ( x varchar2(4000) );

and a db_block_size of 2048. If your column x goes over 1,000 and some odd bytes -- it'll get chained regardless of pctfree and pctused.

OTOH, if my db_block_size is 8192, column x might never get chained even at 4,000 bytes if my pctfree and pctused are set appropriately.

If your block size is smaller then your max rowsize, chaining is a fact of life.

--
See http://govt.us.oracle.com/~tkyte/ for my columns 'Digging-in to Oracle8i'... Current article is "Part I of V, Autonomous Transactions" updated June 21'st  

Thomas Kyte                   tkyte_at_us.oracle.com
Oracle Service Industries     Reston, VA   USA

Opinions are mine and do not necessarily reflect those of Oracle Corporation Received on Fri Aug 13 1999 - 07:17:16 CDT