Re: Table allocates space on empty columns?

From: Peter Sharman <psharman_at_us.oracle.com>
Date: Mon, 01 Feb 1999 12:05:58 -0800
Message-ID: <36B60926.F0C6DCB7@us.oracle.com>

Tom

Just to be a bit picky, it results in MIGRATED rows, not CHAINED rows. Migrated rows start their life in one block, then move to another as you've described. Chained rows are rows that are too big to fit in one block, so part of the row is one block, with a pointer to the next block the rest of the row starts in, and so on.

Pete

Tom Pall wrote:

> Be careful about columns which are empty upon insert but have data
> placed in them during updates. This can result in chained rows, which
> degrades performance. If rows are updated so that there is not enough
> room in the block to hold them, Oracle will continue a row in the next
> block. If your application inserts rows with empty columns which are
> later filled, read about using PCTINCREASE in the Server Concepts manual
> to avoid this.

Regards

Pete

Peter Sharman                              Email: psharman_at_us.oracle.com
WISE Course Development Manager            Phone: +1.650.607.0109 (int'l)
Worldwide Internal Services Education               (650)607 0109 (local)

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Received on Mon Feb 01 1999 - 14:05:58 CST