RE: Locally managed tablespaces - autoallocate vs. uniform
From: Allen, Brandon <Brandon.Allen_at_OneNeck.com>
Date: Fri, 31 Jul 2009 10:45:09 -0700
Message-ID: <64BAF54438380142A0BF94A23224A31E112912C66A_at_ONEWS06.oneneck.corp>
I think that depends on how you define "fragmentation". If you define it as having small extents that can't be used because they're smaller than the next extent sizes of your objects, then I don't think it's even possible with system-managed extents (i.e. AUTOALLOCATE) - I believe autoallocate is smart enough to make use of smaller-than-desired extents if it has to when the tablespace is full, and this is something that UNIFORM cannot do. This is documented, along with some other discussion in favor of using AUTOALLOCATE, in the white paper "ORACLE9I SPACE MANAGEMENT DEMYSTIFIED" available in Metalink 247752.1.
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Date: Fri, 31 Jul 2009 10:45:09 -0700
Message-ID: <64BAF54438380142A0BF94A23224A31E112912C66A_at_ONEWS06.oneneck.corp>
I think that depends on how you define "fragmentation". If you define it as having small extents that can't be used because they're smaller than the next extent sizes of your objects, then I don't think it's even possible with system-managed extents (i.e. AUTOALLOCATE) - I believe autoallocate is smart enough to make use of smaller-than-desired extents if it has to when the tablespace is full, and this is something that UNIFORM cannot do. This is documented, along with some other discussion in favor of using AUTOALLOCATE, in the white paper "ORACLE9I SPACE MANAGEMENT DEMYSTIFIED" available in Metalink 247752.1.
Regards,
Brandon
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Mark Brinsmead
Fragmentation of free space is impossible with uniform extent sizes. It is merely rare with automatic extent sizes, but definitely achievable.
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