Below are some common questions DBAs new to data
warehousing may encounter.
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Q. When should I consider a data warehousing solution?
A. When users are requesting access to a large amount of historical information for reporting purposes, you should strongly consider a warehouse or mart. The user will benefit when the information is organized in an efficient manner for this type of access.
Q. DBAs have always been told that having non-normalized data is bad. Why is it now okay?
A. Normalization in relational databases results in an efficient use of database storage. Data warehousing is not concerned with accomplishing the same storage efficiencies. The main concern is to provide information to the user as fast as possible. Because of this, stroring information in a denormalized fashion, including aggregate columns and summarization, provides the best immediate results.
Q. What is the difference between data warehousing and OLAP?
A. These two terms are often used interchangeably. Warehousing is primarily the organization and storage of the data such that it can be analyzed easily. OLAP deals with the particulars of the process on analyzing the data, managing aggregations, and partitioning information into cubes for in-depth visualization.
Q. How often should I load data into my warehouse from my enterprise transaction systems?
A. The answer to this question may depend on the needs of the users and the volume of information that it is to be moved. It is common to schedule weekly or monthly dumps from the operational data stores, during periods of low activity (for example, nights or weekends). The longer the gap between load, the longer processing times for the load when it does run. You will have to weigh the implications of each to come up with an ideal solution for your situation.
Q. How do I get started with data warehousing?
A. Build one! The easiest way to get started with data warehousing is to analyze an existing OLTP database and see what type of trends would be interesting to examine. From there you could model your new schema and load it with some current data. Although it may seem trivial, it is not. Start small and build from there. SQL 7.0 offers excellent tools and technologies for starting any warehousing effort.
This FAQ is taken from "Microsoft SQL Server 7.0 DBA Survival Guide" by SAMS.
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7/4/2007 6:20:13 AM: 
