Re: ASSM vs. non-ASSM

From: Randolf Geist <>
Date: Thu, 26 Jan 2012 12:27:45 -0800 (PST)
Message-ID: <>

On 26 Jan., 18:06, Mladen Gogala <> wrote:
> I was actually looking for any argument against ASSM. The app to be
> converted uses 8i philosophy with uniform extents and manual segment
> management. As a result, there is a genuine tablespace zoo. Indexes and
> data are separated, a relict from the good old times when DBA could
> specify disk devices, and the tablespaces are divided in 3 categories, S,M
> and X. There is a bitter opposition to the idea of having auto-allocate
> tablespace with ASSM, one for each logical part.
> I wonder what kind of argument can be made in favour of such 8i
> organization, disguised as 10G database? So far, no argument has been
> presented to me, that's why I'm asking.

I know that this is all quite confusing, but you can have autoallocate  with MSSM, or vice-versa uniform extents with ASSM.

Therefore I'm not sure what arguments you're looking for? Are you specifically thinking about how Oracle manages free space within a segment (MSSM vs. ASSM) or is this a discussion related to extent management (auto-allocate vs. uniform)?

Regarding ASSM: Like all "automatic" things it has its quirks and a surprising number of corner cases where it behaves (vastly) differently from MSSM.

Nevertheless the route ahead is clear: Many new features will only be supported/coded with ASSM, so if you think that you want to take advantage of bigfile tablespaces, shrink space, securefile LOBs etc. then you can only use them with ASSM.

Furthermore if you want to benefit from the concurrency enhancements that are built into ASSM and don't want to fiddle manually with freelists and/or freelist groups of MSSM, then again ASSM seems to be the right choice.

If both of above is not that important to the specific situation I would stick to MSSM. Note: For highly concurrent systems (which means an assumed concurrency of many more than 16 concurrent accesses to the same area of a segment) a manually tuned MSSM configuration might perform better than ASSM.

Hope this helps,
Randolf Received on Thu Jan 26 2012 - 14:27:45 CST

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