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Re: table size not true with dba_segments??

From: ffanchy <tirboisf_at_yahoo.com>
Date: 28 Mar 2007 06:35:33 -0700
Message-ID: <1175088933.075186.293770@n76g2000hsh.googlegroups.com>


On Mar 28, 2:42 pm, "Charles Hooper" <hooperc2..._at_yahoo.com> wrote:
> On Mar 28, 8:08 am, "Carlos" <miotromailcar..._at_netscape.net> wrote:
>
>
>
> > On 28 mar, 13:47, "ffanchy" <tirbo..._at_yahoo.com> wrote:
> > > On my opinion, in each case, you can do better job manually than using
> > > automatic management of extends.
>
> > > However unless you want to spend at least 1 day per week managing all
> > > this it is quiet better to use automatic management of extend.
>
> > > I am using it on an OLTP database with arround 2000 tables and 150 Go
> > > RAC on 9i database. It is working fine.
>
> > > Automatic management is using bitmap to manage extends instead of
> > > dictionnary, it is fastter and recommanded by Oracle.
> > > (If you are creating a new database try also to use the automatic
> > > freelist management parameter EXTEND MANAGEMENT LOCAL.
> > > With this parameter only the PCTFREE parameter has to be set all the
> > > others are managed by Oracle. This let you time for other stuffs.
> > > It is also quicker as freelists are manage by bitmap in the first
> > > block of the extend ).
>
> > I think you are a little bit confused between LMT (Locally Managed
> > Tablespaces) and ASSM (Automatic Segment Space Management). LMT have
> > nothing to do with freelists. (Ah! And LMT manage EXTENTS, no
> > "extends").
>
> > Cheers.
>
> > Carlos.
>
> Carlos is of course correct. Locally managed tablespaces are
> preferred to dictionary managed tablespaces, as there is less
> performance impact from the overhead required for Oracle to maintain
> locally managed tablespaces compared to dictionary managed
> tablespaces. Additionally, locally managed tablespaces can be created
> such that all objects placed into the tablespace have a consistent
> extent size, regardless of the extent parameters that are specified
> for the objects.
>
> ASSM removes the need for managing freelists, as well as managing
> extent sizes. As additional extents are added for objects, the new
> extent increase in size in a predictable fashion. One of the
> downsides of ASSM is that it can potentially hurt performance, as it
> artifically increases the clustering factor of indexes due to the way
> that it decreases insert contention on the objects placed into such
> tablespaces. There are many great articles that decribe this behavior
> in greater detail.
>
> Charles Hooper
> PC Support Specialist
> K&M Machine-Fabricating, Inc.

I have checked few stuff and I was wrong.

Regading LMT, activation is done by : EXTENT MANAGEMENT LOCAL Regading ASSM, activation is done by : SEGMENT SPACE MANAGEMENT AUTO Received on Wed Mar 28 2007 - 08:35:33 CDT

Original text of this message

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