Re:ASSM and tablespace fragmentation
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 26 Sep 2007 14:10:00 +0100
I suspect you mean allocation_type= 'SYSTEM' which is
about the gradual changes in extent sizing as the object
grows, rather than ASSM which is about using bitmaps
in segment headers and at the start of extents to represent
the state of blocks rather than using freelists.
If that's what you had in mind, then the following URL
may be useful.
http://jonathanlewis.wordpress.com/2007/05/29/autoallocate-and-px/
If this is what you were thinking of then you probably are better
off with uniform extents as you know the size of the data and can
set a sensible extent size.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
Author: Cost Based Oracle: Fundamentals
http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
----- Original Message -----
From: ryan_gaffuri@xxxxxxxxxxx
Subject: ASSM and tablespace fragmentation
Date: Wed, 26 Sep 2007 03:51:07 +0000
There was an article written a few years ago talking about certain cases where
you can have tablespace fragmentation when using ASSM. I think Niall
Litchfield wrote this(I could be wrong). I believe this was due to deletes. I
am not using deletes, but will be dropping alot of partitions and am wondering
whether I may have problems with this down the road. Here is my scenario.
1. initally go to production with 500 GB of data
2. This will grow to between 25-50 TBs over 15 months.
3. We will load 1/10th of the data/day into the database. So at 500GB we will
load 50 GBs/day at 25-50 TBs we will load 2.5 - 5 TBs/day.
4. tables are partitioned by date with hourly partitions.
5. We will drop partitions that are 10 days old.
So we are recycling data every 10 days while our database size is growing.
Does this scenario have any risk of tablespace fragmentation with ASSM? We may
use ASM, but I don't think that matters in this case.
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