Re: Does the number of extents affect the performance?

Ian Cary wrote:
>
> Although I agree that in general having multiple extents does not affect
> performance, I still think it is important to attempt to size tables
> correctly as I believe for insert purposes there is an overhead in the
> creation of new extents.
> Also unless I am deliberately trying to partition my data over more than
> one disk I like to see a tables blocks being contiguous within a
> tablespace (mainly for aesthetic reasons I'm afriad)
>
> Ian

The overhead occurs when a new extent is created i.e. for 1 inserted row per 10,000 (say). This might occasionally be important in real-time data-acquisition systems.

The best reason for sizing tables correctly is to ensure that the maximum number of extents is never exceeded.

You don't need to be "afraid" of aesthetic reasons. Good-looking systems are fine, so long as the effort involved in maintaining prettiness does not itself cause performance degradation.

Any way, I hope that the myth of multiple extents being the cause of bad performance has finally (?) been laid to rest.

-- 
Chrysalis

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('To Protect and to Serve')
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