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Re: Oracle Concepts Question

From: Ron <support_at_dbainfopower.com>
Date: Sat, 7 Feb 2004 11:47:50 -0800
Message-ID: <PYKdneruv9bzorjd4p2dnA@comcast.com>

"When a table has more than 255 columns, rows that have data after the 255th column are likely to be chained within the same block. This is called intra-block chaining. A chained row's pieces are chained together using the rowids of the pieces. With intra-block chaining, users receive all the data in the same block. If the row fits in the block, users do not see an effect in I/O performance, because no extra I/O operation is required to retrieve the rest of the row."

 Hope this answers the question.

Regards,

Ron

DBA Infopower

http://www.dbainfopower.com

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"RK" <rajXesh_at_hotmail.com> wrote in message news:548b9514.0402061242.64b4b0dd_at_posting.google.com...
> I was reading the Concepts manual and was puzzled by this sentence.
> Can anyone elaborate on this:
>
> <snip> Tables are the basic unit of data storage in an Oracle
> database. Database tables hold all user-accessible data. Each table
> has columns and rows. Oracle stores each row of a database table
> containing data for less than 256 columns as one or more row
> pieces.</snip>
>
> What is this 256 column limit. I thought row chaining / migration
> depended on row size.
>
>
> See

 http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96524/c01_02intro.htm#20658
>
>
> Thanks
>
> rajXesh
Received on Sat Feb 07 2004 - 13:47:50 CST

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