Re: Compressing partitions

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_at_freelists.org 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
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