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Question and Answer

Tom Kyte

Thanks for the question, Tad.

Asked: October 23, 2000 - 6:27 am UTC

Last updated: October 23, 2000 - 6:27 am UTC

Version: 8.0.5

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You Asked

Tom

I'm currently looking at a customers database that is quite large (around 35Gb).

Some of the larger tables (3.5Gb) have been put into their own tablespaces, which is good, but the tables have multiple extents (around 35 - 50). This is also true of the indexes which have up to 85 extents.

Currently the customer is happy with this as they say the datafiles exist on a RAID 5 array and that the extents do not make a difference, as they would if they were on a single physical disk.

The question is : Is it better to have the tables in a tablespace in one (or two) extents on a RAID 5 device, or is it okay to let it extend thus enabling multiple reads from different parts of the tablespace ?

I would rather have minimal extents as I have always believed that this offers better performance. Am I wrong ?

Thanks,

Tad

and Tom said...

It is a MYTH.

Go for many extents. It cannot, willnot, does not, affect performance with the exception of certain DDL operations (such as DROP or truncate).

See
</code> http://asktom.oracle.com/pls/asktom/f?p=100:11:::::P11_QUESTION_ID:421419463648 <code>...


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Comments

Running across this same issue.

Mike Porter, March 06, 2006 - 1:30 pm UTC

We are running some automatic monitoring software that
started emitting warning about too many extents (300).
It is nice to know that these warnings are based on a myth.

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