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How does Oracle allocate a new extent ? [message #175869]

Mon, 05 June 2006 15:35

agostino_neto
Messages: 180
Registered: July 2005

Senior Member

Hi all,

I have noticed that when a new datafile is added to the database. Extents are not always created from the top to the bottom of the file.
When querying dba_extents, dba_data_files and dba_objects, I can see that sometimes newer extents begins at a smaller block than the previous one. How does Oracle allocate a new extent and for what reason ?
Thanks.

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Re: How does Oracle allocate a new extent ? [message #175905 is a reply to message #175869]

Tue, 06 June 2006 00:29

shahnazurs
Messages: 240
Registered: June 2005
Location: India

Senior Member

Hi,
you said you created one datafile i.e. you created logical structure called tablespace!
different types of extent management present in oracle 9i, one is dictionary management & other one is local...
could you please let me know which version of oracle you are interested?

Thanks,
Shahnaz

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Re: How does Oracle allocate a new extent ? [message #175968 is a reply to message #175905]

Tue, 06 June 2006 04:17

agostino_neto
Messages: 180
Registered: July 2005

Senior Member

I am currently using Oracle 8.0.6

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Re: How does Oracle allocate a new extent ? [message #176061 is a reply to message #175869]

Tue, 06 June 2006 13:15

smartin
Messages: 1803
Registered: March 2005
Location: Jacksonville, Florida

Senior Member

It is a "not documented", internal, proprietary, "subject to change" algorithm based on version and on oracles whim. You control which objects are assigned to which tablespaces, and oracle divides data from a single tablespace throughout the datafiles in that tablespace however oracle sees fit.

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Re: How does Oracle allocate a new extent ? [message #176068 is a reply to message #176061]

Tue, 06 June 2006 14:40

agostino_neto
Messages: 180
Registered: July 2005

Senior Member

Does Oracle use B-tree algorithms in 9i or 10g ?

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