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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Datawarehouse Sizes.....informal poll.
Ross - Still hung up on size hmmm.
How about this for a definition. A data warehouse encompasses data for the entire organization. A data mart services data for a portion of the organization.
The history of this subject is relevant. In the 80's there were Executive Information Systems. Systems couldn't host much data then, but these were an attempt to have the relevant data the executives needed to make decisions. This didn't pan out.
Then in the 90's came the Data Warehouse movement. Put all the data for the entire organization into a single database. Problem was that people spent years squabbling over the design and by the time the data warehouse was built, the business had evolved and the data warehouse wasn't very relevant. Some warehouses were successful, but many were not. This made everyone skittish about claiming they had a data warehouse.
Meanwhile, some departments got tired of waiting and created their own. These came to be called data marts. Many of these data marts were able to show immediate results, so "data mart" sounds nice.
As to size, the data marts at one organization may be larger than another organization's data warehouse.
But as data marts matured, problems emerged. One data mart is great, but when an organization has dozens, you can get different results from different data marts because they were built with different data models, extract data at different times, and treat data differently. And if each data mart separately extracts data from the operational systems, this causes a lot of overhead.
Now the whole field of data warehousing has matured. People that build them realize that warehouses aren't simple to build and there is more tolerance from management as to the effort required. And many organizations are seeing significant benefits.
Ross - well that is about the limit of my knowledge. I don't know where you
are heading with the warehousing, but I would highly recommend the
mailto:dwlist-request_at_datawarehousing.com list. There are some real experts
on that list (even Ralph Kimball participates from time to time), yet they
are amazingly tolerant of newby questions.
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
-----Original Message-----
Sent: Thursday, December 06, 2001 9:00 PM
To: Multiple recipients of list ORACLE-L
Jared,
Thanks. I have the main RK book. Like it. Understand what little i have read of it. I am just interested in what folks thought about "size vs. DW definition" was.
I *do* think, tho, that "size does matter".
I don't consider my shared E: drive a datawarehouse because it can support a star query, one user, and 300 MB of data.
There is 'something' to do with the fact of...alot of data....skewed dimensions...regular updates...data cleaning...supporting mining ( and mining for a few tiny facts in a big haystack requires, after all, the big haystack )
Anyways.
I figure anything under 250 GB doesn't even merit being called a data Warehouse.
Maybe a data 7-11. <shrug>
Thanks for the pointers and your thoughts.
Ross
-----Original Message-----
To: ORACLE-L_at_fatcity.com
Cc: MohanR_at_STARS-SMI.com
Sent: 12/6/2001 7:32 PM
Ross,
A DW is defined by purpose and design, not by size.
A collection of Data Marts, ( tables for star joins ) is not a DW either. DW's are used to create data marts.
If you don't already have the database books from Kimball, I suggest you acquire them.
Data Warehouse Toolkit
http://www.amazon.com/exec/obidos/ASIN/0471153370/ref=pd_sim_books/104-7
669992-7054323
Data Warehouse Lifecycle Toolkit
http://www.amazon.com/exec/obidos/ASIN/0471255475/ref=pd_sim_books/104-7
669992-7054323
These are must haves for understanding and designing DW.
Jared
"Mohan, Ross"
<MohanR_at_STARS- To: Multiple recipients of
list ORACLE-L <ORACLE-L_at_fatcity.com>
SMI.com> cc:
Sent by: Subject: Datawarehouse
Sizes.....informal poll.
root_at_fatcity.c
om
12/06/01 01:55
PM
Please respond
to ORACLE-L
Informal survey: Datawarehousing.
Limiting Assumption: "A necessary and sufficient condition for
defining
something
to be a datawarehouse is the
amount of data
Question/Poll: Given the above ridiculous constraint, at/above what
size
can something
be considered a data
warehouse?
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Author: Mohan, Ross
INET: MohanR_at_STARS-SMI.com
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