Re: Datawarehousing help

Hello Dennis

SAS has progressed a little in the last years and now offer a complete DW solution, including ETL tools.

You can use their tools also to populate and query oracle.

Yechiel Adar
Mehish

• Original Message ----- To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Sent: Saturday, May 04, 2002 2:48 AM

> Rachel - I always find it helpful to understand something if I know the
> origins. I worked with SAS several years ago. At that time it was a
> statistical analysis package. A scientist or engineer could load a set of
> test data into it and perform various arithmetic and statistical analyses.
> Today most of that can be done with Oracle or MS Excel. My point is that I
> would expect it to be heavily biased toward mathematical capabilities.
Like
> Data Mining, which is all statistics. Learn what that term means.
> To learn Data Warehousing, I would encourage you to just do some
> "Googling" and find good tutorials. An excellent newslist is dwlist.
> Instructions:
>
> For help with list commands, send a message
> to <mailto:dwlist-request_at_datawarehousing.com> with the
> word "help" in the body of the message.
>
> The magazine http://www.intelligententerprise.com/ has some excellent
> information. I would search for "Ralph Kimball". He is one of the leading
> figures in the DW arena. Look for some of his earliest columns on the
> magazine site. He also answers questions on dwlist from time to time.
>
> The main change you need yourself is to forget normalization. DBAs that
> can't get past that point don't last long in the DW field. In the early
days
> the DW people would patiently explain the reasons to a DBA, but today
there
> are enough DBAs that have made the leap that a hard-headed normalization
> bigot just isn't tolerated. It is much easier to just ask for a
replacement
> DBA.
> The reason normalization isn't adhered to in DW is that users will
> be creating their own queries and they can't understand 10-table joins
with
> outer joins, etc. A DW is usually loaded and then queried. Our DW is
loaded
> each weekend and then queried all week. So a DW is deliberately
denormalized
> and contains redundant data for ease of use.
> OLTP databases have no concept of "time". A DW is all about time. To
> reconstruct what the situation is at various points of time, the DW has
> loads of historical data. For example, marketing people need to be able to
> reconstruct the amount of business they did with a customer over a period
of
> time last year and compare it with the same period this year.
> So between denormalization and tons of detailed historical data, DWs
> are normally BIG! Fortunately they are usually read-only.
> For Oracle, you want Enterprise Edition with the partitioning
> option. And study Oracle Materialized Views.
> In schema, a DW is usually a central fact table and 4-6 dimension
> tables. Less than 4 dimensions and you don't need a DW. More than 6 and
> marketing people can't understand the model. Normally the fact table is
much
> larger than the others, but not always. One of Wal-Mart's dimension tables
> is each person in the U.S. Just size each of those tables, and you've got
> your size. Growth is easy to predict. Ralph Kimball warns that often
people
> will get the grain wrong. They will size it for data summarized at the
> weekly level, then after it is built they will realize that isn't going to
> cut it and need a daily level. You must start almost from scratch and get
7
> times the disk capacity. That is the fun side of being a DW DBA. Your
> cynical instincts will still serve you well, just get them away from
> normalization and worry about getting the grain right.
> Okay, I've rambled along here too long. Hope that gets you off on
> the right foot.
>
> -----Original Message-----
> [mailto:Rachel_Carmichael_at_Sonymusic.com]
> Sent: Friday, May 03, 2002 5:08 PM
> To: Multiple recipients of list ORACLE-L
>
>
>
>
> Okay, my background is OLTP, but we are looking at a data warehousing
> project
> here....
>
> any and all help appreciated! Specifically:
>
> 1) does anyone have any experience with a product called "SAS
> Datawarehousing
> Administrator" (or SAS)?
> 2) how do I go about doing rough estimates of sizing needs, assuming I
will
> get
> rough numbers of information being collected, growth rates, length of
> history to
> keep, etc.
>
> help?
>
> Rachel
>
>
> --
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> Author:
> INET: Rachel_Carmichael_at_Sonymusic.com
>
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> Author: DENNIS WILLIAMS
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Yechiel Adar
  INET: adaryechiel_at_hotmail.com

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