Re: How SEG$ is updated in DMS
- From: Niall Litchfield <niall.litchfield@xxxxxxxxx>
- To: hkchital@xxxxxxxxxxxxxx
- Date: Tue, 1 Feb 2005 09:17:17 +0000
On Tue, 01 Feb 2005 11:12:22 +0800, Hemant K Chitale
<hkchital@xxxxxxxxxxxxxx> wrote:
>
> While running a large CREATE INDEX using a Tablespace Temporary which is
> Dictionary Managed,
<snip sql>
> At this stage, it is still creating the Temporary Segment. Why does it have
> to update ALL the columns of SEG$
> for each Extent being allocated ? No wonder that DMS Temporary Tablespaces
> are called "slow".
I don't believe that it is *creating* the temporary segment, I believe
that it is *allocating* extents for use during the sort. (it could of
course be allocating extents to the index itself - one would need to
see the values of the binds).
That is my understanding of the *temp* usage during this operation is
1. create temp segment (at min size)
2. use temp segment as required to sort data - this may involve new
extent creation/allocation
3. mark extents reusable after use.
--
Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com
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