RE: ASSM and high volume concurrent inserts

From: Mark W. Farnham <>
Date: Thu, 17 Dec 2009 19:20:54 -0500
Message-ID: <>

By DMT do you mean dictionary managed? That is certainly not required to use "manual" aka freelists segment space management. A locally managed tablespace can be ASSM or freelists in all versions I'm aware of.

extent management dictionary
extent management local autoallocate
extent management local uniform [SIZE <size_clause>]

are the extent management possibilities


segment space management auto
segment space management manual

are the segment space management possibilities. If you specify extent management dictionary, you get segment space management manual. (And does anyone think dictionary managed tablespaces are ever a good choice any more? IF you do, please let me know when and why - and avoiding a full export import to get rid of dictionary management of an existing SYSTEM tablespace I don't really count as a "choice.")

You're probably confused by the statement "The segment_management_clause is relevant only for permanent, locally managed tablespaces" in the manual. That is true, but only because ASSM is not available for dictionary managed tablespaces.



-----Original Message-----
From: [] On Behalf Of FMHabash
Sent: Thursday, December 17, 2009 6:15 PM To:; Subject: RE: ASSM and high volume concurrent inserts

Not sure what you mean by 'manually managed'. To manage FLists yourself, you need a DMT TS, which I believe can't do in 10g (for read/write). We had a similar problem on a high frequency LOB insert, which we resolved by eliminating a composite unique constraint. About 90% of BBW's that I've seen resulted from poor application design or run-time anomalies.
Focus on application design and run-time behavior before you start thinking tablespace and segment attributes.

-----Original Message-----
From: Haroon A. Qureshi <> Sent: Thursday, December 17, 2009 12:46 PM To:
Subject: ASSM and high volume concurrent inserts


A client is running an application that does high volume concurrent inserts
(> 200million rows). Performance degrades with high buffer busy waits. The
tablespace is ASSM managed, so we can't change the freelists to tune it. I want to try moving to a manually managed tablespace and tune the freelists. But not sure if the client will go for that change, given the effort and timelines. Has anyone come across performance issues with ASSM and high volume inserts? Anyway of tuning it with ASSM?

Thanks in advance,



Received on Thu Dec 17 2009 - 18:20:54 CST

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