Re: Table with 300 columns (ie > 255) : Row Chaining ?

From: Christian Antognini <>
Date: Tue, 20 Oct 2009 20:40:32 +0200
Message-ID: <>

Hi Hemant

> I didn't know that. Also, the splilt at the 96th column was the
> surprise. Why 96 ?

Your test table has 350 columns. A row piece can store at most 255 columns. As a result, you have two row pieces: one with 255 columns and another with 95 (350-255) columns. As I wrote in my previous reply, the pieces are split and stored in "reverse order". That means two things: 1) the first row piece is the one having 95 columns 2) the first row piece is stored after the second one.

> What if the table has 250 columns ? Then it is a single row piece
> without a split ?

If it fits in a single block and it is not subject to row migration, it is stored in a single piece.

Chris Antognini

Troubleshooting Oracle Performance, Apress 2008

Received on Tue Oct 20 2009 - 13:40:32 CDT

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