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Thursday, April 21, 2011

Steps to develop a Cube in SSAS...

Before we start with the cube development, there are a few things that should be discussed. As we know that the cubes are developed on OLTP databases that are de-normalized. You should be having a complete understanding of your existing OLTP database and the reporting requirements for which you are planning for SSAS cube. This is done to get maximum performance from them. Also, It is easier for the cubes to make aggregates against the data. So;

1.   Check and list down the tables for your Diemnsions in your OLTP production database.
2.   Check and list down the tables for Facts in your production database.
3.   In addition to all the dimensions, you will be needing a Date dimension and Time dimension.
4.   Create a separete OLTP database for the above listed Dimensions and Facts. You can also call this database as your Staging database.
5.   Name Dimension tables with "DIM" at the end or Statr so that you can easily identify them.
6.   Name Facts table with "Fact" at the end for easy identification.
7.   De-normalize your Dimension tables in a way that you can create buit-in hirarchies. 8.   You Fact tables should contain factual information(Quantities, Amounts, etc) along with the foreign keys with the tables that you have created as Dimensions in your New OLTP database.

9.   Define Primary keys and foriegn keys as required.
10. Write down the scripts to initialize your Staging Database with the data in your production database. I would recommend that you take backup of your production database and restore at the same serber where you have creted your Staging database. Work on that copy of the production database and DO NOT work directly on your production database on production server.
11.  Verify the data ported by scripts.
The purpose of the Staging database are multiple. While porting your normalized data to de-normalized database, you might findout some missing or incomplete data. This issue especilly rises for dates, times and names. You can clean your data in here using data cleansing procedures according to your requirements.
Follow the above mentioned steps to create and populate the staging database and prepare your self for creating cube on this database.

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