Re: Compressing partitions
- From: Tanel Põder <tanel.poder.003@xxxxxxx>
- To: "ORACLE-L" <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 4 Jul 2005 13:37:06 +0100
Hi,
If you are talking about historical data, which you won't be modifying later
on, I don't see any real downsides with compression, but with frequently
modified OLTP data, yes.
Performancewise, you might want to order your data pysically according your
main index used in range scans on table as well, that way range scans using
this index will me more efficient as table rows are physically clustered in the
order of your index (if performance isn't an issue, then don't bother).
If you want to do physical row ordering, then that's one way to go:
create table temp nologging compress as select * from your_table partition p1
order by col1,col2,col3;
create index i1 on temp(col1,col2,col3) nosort nologging compress x;
create other indexes... w compress option
alter indexes back to logging (if you want to, for maintenance reasons)
alter table your_table exchange partition p1 with table temp including indexes
without validation;
alter table your_table modify partition p1 logging;
Also, a very interesting article regarding efficient partition exchanging is
http://www.dbazine.com/oracle/or-articles/jlewis17
Tanel.
----- Original Message -----
From: Kline.Michael
To: oracle-l@xxxxxxxxxxxxx
Sent: Monday, July 04, 2005 2:57 AM
Subject: Compressing partitions
We have several large 2-4 gig partitions on a 5 year basis. After a month or
two, changes should be almost non-existent.
They also have partitioned indexes. Just makes things easier when we roll off
the oldest partition, etc.
Is there a downside to compression?
It's sounds like it's supposed to be more stable now, handling tables and
indexes.
While I've not found much, it seems like we could expect the 2-4 gig to maybe
be 200-400 meg??? Even if 25-50% would not be bad given some of it is 5 years
history.
We are at 9.2.0.6.
Michael Kline
Database Administration
SunTrust Technology Center
1030 Wilmer Avenue
Richmond, Virginia 23227
Outside 804.261.9446
STNet 643.9446
Cell 804.744.1545
michael.kline@xxxxxxxxxxxx
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