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Extents and blocks [message #326587]

Thu, 12 June 2008 01:24

aslamkhalife
Messages: 42
Registered: July 2007
Location: India

Member

Hi

I have few queries regarding EXTENTS

1. Why large object should have uniform extent size?
2. Why small object should be place in auto allocate?
3. Exactly what will be the large and small object size in Oracle?
4. How can one decide the size of uniform extent clause?
5. How does the block and extent work in Oracle?

Please guide....

Aslam

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Re: Extents and blocks [message #326608 is a reply to message #326587]

Thu, 12 June 2008 02:04

Michel Cadot
Messages: 68729
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

1. No reason, "should" is wrong.
2. No reason, "should" is wrong. It is just easier to manage
3. What you want, it is not an Oracle notion
4. As you want, the best is to not use it, use autoallocate
5. See Database Concepts

Regards
Michel

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Re: Extents and blocks [message #326624 is a reply to message #326608]

Thu, 12 June 2008 02:19

aslamkhalife
Messages: 42
Registered: July 2007
Location: India

Member

Hi,

Presently one our DEV db has the autoallocate = system
It means the initial extent size is by default 64kb and the PCTINCREASE is by default 50, which result in next extent to be much more larger to initial one and also further the extent size goes on increasing........
because of this space is been wasted......

Now how can I stop this wastage.......

Thanks
Aslam.

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Re: Extents and blocks [message #326696 is a reply to message #326624]

Thu, 12 June 2008 05:25

Michel Cadot
Messages: 68729
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

Quote:

It means the initial extent size is by default 64kb and the PCTINCREASE is by default 50

This is wrong.
system/autoallocate means Oracle chooses the size.

Regards
Michel

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Re: Extents and blocks [message #327532 is a reply to message #326587]

Mon, 16 June 2008 15:41

JackyShu
Messages: 25
Registered: May 2008

Junior Member

uniform extent size to avoid fragments, but of course, if you set huge extent size for a small table, space might be wasted. Laughing

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Re: Extents and blocks [message #327569 is a reply to message #327532]

Mon, 16 June 2008 23:24

Michel Cadot
Messages: 68729
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

Quote:

uniform extent size to avoid fragments,

Autoallocate too.

Regards
Michel

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Re: Extents and blocks [message #327575 is a reply to message #326587]

Mon, 16 June 2008 23:51

aslamkhalife
Messages: 42
Registered: July 2007
Location: India

Member

Hi Michel,

I dint understand you last reply....

"Quote:
uniform extent size to avoid fragments,
Autoallocate too."

Regards
Aslam

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Re: Extents and blocks [message #327601 is a reply to message #327575]

Tue, 17 June 2008 00:41

Michel Cadot
Messages: 68729
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

Autoallocate/system allocation also prevent from fragmenting as well as uniform.
Assuming "fragmenting" means leaving never used free holes.

Regards
Michel

[Updated on: Tue, 17 June 2008 00:42]

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