Understanding Dimension Basics Page - 2

The Dimension Editor Interface

In the second tutorial of the series “Introducing Analysis Manager Wizards” we used dimension wizards to build our dimensions. The dimension editor however, appeared as soon as the dimension was created. This is because the Dimension editor is the interface that helps the user manipulate and edit a dimension. In the Analysis Manager, the main console, the Dimension Editor, and the Cube Editor are the only three windows. All others are wizards or dialog boxes.

Before proceeding to actually building dimensions let us examine the Dimension Editor interface we will be using. It consists of two panes—the left pane with the dimension tree and the properties pane and the right pane displaying the dimension tables with two tabs called schema tab and data tab.

The Dimension Tree Pane

The dimension, its levels and member properties are contained in the Dimension tree pane that appears on the left pane of the Dimension editor interface. Clicking on the dimension name in the tree will activate the dimension level properties. For instance clicking on Store in the dimension tree will activate the properties of the store dimensions and the members will be displayed on the right pane. To delete a member level the user has to right click on the member and select delete. To rename a level, the user will have to click on the dimension level and click Rename. The name can then be altered. Using “Altering the name property” for that dimension level will also change the name of the property.

The schema of the dimension is displayed in the schema tab of the Dimension editor. This interface displays the tables, views and joins of the relational database that has been used to create the dimension. This schema is extremely useful where snowflake schema or parent child dimensions have to be created.

The Data tab of the interface enables the user browse the hierarchy of the dimension. Custom member formulas are displayed in a small window in the right pane and the type of member properties used and the values of the member properties within the dimension member.

The Custom member formula window in the bottom right corner of the data tab allows the user to create a calculation at the member level. These calculations are useful in instances where the members created are based on other dimension members. For instance in a financial budget for current year’s expenses a 20% increase can be made by creating a custom calculation at the member level so that Current year’s Budget member is 1.2 times the Current year’s actual member. Calculation at member level requires that the SQL Server Enterprise edition is in use and the write back to the dimension option is enabled.

Grouping levels is used when a dimension contains more than 64,000 members. In MOLAP storage mode Analysis services can handle up to 10 million members but the number of child members to a parent can be only 64,000. Artificial hierarchies are created to circumvent this problem. Analysis services has an inbuilt option of automatically creating the artificial hierarchies. For instance in the Employee dimension “all employees” would be a artificial hierarchy.