Oracle-L: RE: Using dimensions

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Mon, 29 Sep 2003 11:59:40 -0800
Message-ID: <F001.005D1639.20030929115940@fatcity.com>

Raj - There is some melding of DW and OLTP environments at some sites today. Most DW's are separate environments with data extracted from the OLTP on a regular batch schedule. But it is possible to have a combined environment that satisfies both requirements, especially if you are starting from scratch and not trying to add DW to an existing system. If your users require "real-time" DW queries, this may be a better alternative.

The biggest problem I've heard is the Oracle buffer cache. After it has been running awhile the OLTP buffers will tend to hold the hot blocks. By definition, a DW doesn't have hot blocks, so if both OLTP and DW share the same instance, the DW will tend to mess up the buffer cache for OLTP, so OLTP performance will suffer. Of course, a combination schema design may satisfy nobody, but we DBAs are used to dealing with unhappy people.

Dennis Williams
DBA, 80%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Monday, September 29, 2003 1:50 PM To: Multiple recipients of list ORACLE-L

Thanks Dennis ...

We have "a" group who design their application as if this is a DW environment, so I thought learning this stuff might be beneficial for "me".

I'll check it out.
Raj

Rajendra dot Jamadagni at nospamespn dot com All Views expressed in this email are strictly personal. QOTD: Any clod can have facts, having an opinion is an art !

-----Original Message-----
<mailto:DWILLIAMS_at_LIFETOUCH.COM> ]

Sent: Monday, September 29, 2003 2:25 PM To: Multiple recipients of list ORACLE-L

Raj - Actually a good place to start is the Oracle9i Data Warehousing Guide http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96520/logical
<http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96520/logical
> .
htm#97703
<

http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96520/logical
<http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96520/logical
>
.htm#97703>
I think it is important for all Oracle DBAs to understand the fundamental concepts behind DW. You never know when you'll get yanked into a meeting where they are discussing it and you don't want to say something Neanderthal

like "of course we'll fully normalize the schema". Ralph Kimball has some good materials on his web site: http://www.ralphkimball.com
<http://www.ralphkimball.com>
< http://www.ralphkimball.com <http://www.ralphkimball.com> >

Dennis Williams

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Author: DENNIS WILLIAMS
  INET: DWILLIAMS_at_LIFETOUCH.COM

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Received on Mon Sep 29 2003 - 14:59:40 CDT