Re: LOCALLY MANAGED EXTENT PERFORMANCE

From: Tim Gorman <tim_at_evdbt.com>
Date: Sun, 24 Apr 2005 13:44:32 -0600
Message-ID: <BE915340.26537%tim@evdbt.com>

Exactly why might a large number of extents be a bad thing? In other words, are you sure you are attaching the proper level of importance to the issue?

To help figure out if this is true, can you describe exactly what operations might be affected by the number of extents, and how? Queries? Inserts/updates/deletes? Truncates? Drops? Monitoring queries?

And, are you certain that autoLMT resolves the problem of "too many extents"? Isn't there an upper limit on extent size even with autoLMT? If so, then how is this different from intelligently sized uniform LMTs?

My apologies for the Socratic questioning, but this thread contained too many assertions that need a little more examination...

-Tim

on 4/22/05 11:07 PM, Dogan, Ibrahim - Ibrahim at Ibrahim.Dogan_at_Lowes.com wrote:

> 
> Even with LMTs, you still wory about number of extents whenever you run
> any command that performs extent allocation/deallocation (create
> table/rebuild index/truncate table etc..)
> 
> My point was that I saw many people going back to DMT because of very
> same issue you're experiencing with LMTs.. When LMT with uniform extent
> size is used, you need to babysit the segments to make sure they don't
> go beyong couple thousand extents.. But you don't have this problem if
> you use LMT with AUTO extent allocation. My biggest table is 27G in a
> AUTO LMT and it has around 600 extents..
> 
> I generally prefer AUTO LMT and reorg the tables after bulk deletes...
> 
> 
> Thanks,
> 
> Ibrahim DOGAN
> Sr. Sybase/Oracle DBA
> www.lowes.com
> 
>

>> -----Original Message-----
>> From: Wolfson Larry - lwolfs [mailto:lawrence.wolfson_at_acxiom.com]
>> Sent: Saturday, April 23, 2005 12:55 AM
>> To: Dogan, Ibrahim - Ibrahim; oracle-l_at_freelists.org
>> Subject: RE: LOCALLY MANAGED EXTENT PERFORMANCE
>>
>> And I thought Oracle said you didn't have to worry about how
>> many any more.
>>
>> I didn't exactly blame LMTs I just said there were a
>> lot of extents.
>> Not my app.
>>
>> Thanks for info
>>
>> -----Original Message-----
>> From: Dogan, Ibrahim - Ibrahim [mailto:Ibrahim.Dogan_at_Lowes.com]
>> Sent: Friday, April 22, 2005 11:46 PM
>> To: Wolfson Larry - lwolfs; oracle-l_at_freelists.org
>> Subject: RE: LOCALLY MANAGED EXTENT PERFORMANCE
>>
>> Do not use uniform sized LMTs for volatile tables since you
>> may end up having a table/index with thousand of extents..
>>
>> More important, don't blame LMTs for it..
>>
>> If you use AUTO extent allocation instead of uniform size,
>> you won't have problem...
>>
>> Thanks,
>>
>> Ibrahim DOGAN
>> Sr. Sybase/Oracle DBA
>> www.lowes.com

--
http://www.freelists.org/webpage/oracle-l

Received on Sun Apr 24 2005 - 15:49:12 CDT