| Extent Management [message #120660] |
Sun, 22 May 2005 02:39  |
Eric Langager
Messages: 38
Registered: April 2004
Location: Beijing, China
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My question has to do with how extents are managed by Oracle. I have attached a spool file to illustrate the process I use. First, I create a table called "Numbers." Then I run a script called "insert" which inserts 100,000 rows into the numbers table. When I then view the exents, I get two different results depending on whether I created the table in the System tablespace, or a local tablespace. When created in the System tablespace, the growth of extents is progressive. But when I create the table in the local tablespace, all extents are the same size until Extent #16, when the size jumps dramatically. I would like to know what the setting is that causes this to happen. (Spool File is Attached.)
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Attachment: Extents.LST
(Size: 8.93KB, Downloaded 1016 times)
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| Re: Extent Management [message #120672 is a reply to message #120660] |
Sun, 22 May 2005 10:31  |
Frank Naude
Messages: 4580
Registered: April 1998
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Senior Member |
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Hi,
This is standard behavior for tablespaces created with with "... EXTENT MANAGEMENT LOCAL AUTOALLOCATE;".
Oracle chooses a "sort of optimal" next extent size starting with 64KB. As the segment grows larger extent sizes will increase to 1MB, 8MB, and eventually to 64MB.
To prevent this, use "... EXTENT MANAGEMENT LOCAL UNIFORM SIZE ..." when creating the tablespace.
Best regards.
Frank
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