Re: Does the number of extents affect the performance?

From: Thomas Kyte <tkyte_at_us.oracle.com>
Date: 1997/09/05
Message-ID: <34125df1.8307375@newshost>#1/1

On Fri, 05 Sep 1997 03:28:17 GMT, dtang_at_minn.net wrote:

>Hi:
>
>After reading several articles, I get an imprsssion that the fewer
>extents in a table's data segment, the better the performance would
>be. But I can't find this statement in any official document.
>So I want to ask the experienced DBA about the relation between the
>size of extent and the performance.
>

No, performance for a 1 extent table will be no different then a 100 extent table. this (few extents = better performance) is a rumor.

On many databases, you can run export with compress=y and see a measurable performance improvement in the resulting imported database. The serious flaw with using this data point as a "proof" that few extents is good is that you can use compress=n and achieve identical performance gains. The performance gains come not from reduction in the number of extents in database segments, but from the block packing and row fragmentation removal implicitly in any import.

> Any input will highly be appreciated. Please e-mail me at
>dtang_at_minn.net
>
>Thanks ahead
>
>
>Dong Tang
>
>Dong Tang
>

Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Bethesda MD

http://govt.us.oracle.com/ -- downloadable utilities

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Opinions are mine and do not necessarily reflect those of Oracle Corporation Received on Fri Sep 05 1997 - 00:00:00 CDT