Creating Virtual Dimensions

Analysis Services

Analysis Services

Creating Virtual Dimensions

Virtual dimensions enable you to display categorical labels from a single dimension table on multiple axes in browsers without increasing cube size. (Without virtual dimensions, multiple regular or parent-child dimensions would be required.) Specifically, you can display the members of a dimension level on one axis and an associated attribute (that is, a member property) of those members on the other axis. This presentation is useful when end users want to explore the trends of measures depending on the relationship between members and member properties.

For example, an end user requests to analyze Sales by Product Name and Package Material to explore customers' preferences for recyclable Package Materials. If the Product dimension already contains Product Name, add Package Material as a member property and create a virtual dimension from it. After you add the virtual dimension to the cube, the user can cross-reference Product Names and Package Materials and compare the Sales at the intersections.

The main advantages of virtual dimensions are storage savings and reduced cube processing time. Aggregation data for virtual dimensions is not stored. It is calculated in memory. Therefore, if you add a virtual dimension to a cube, its storage usage and processing time do not increase as when you add a regular or parent-child dimension. All cubes require dimensions, but not all cubes require virtual dimensions.

A virtual dimension is created from member properties or columns of another dimension that is not a virtual dimension. You can add a virtual dimension to a cube only if the dimension that supplies the member properties or columns is also included in the cube. To create a virtual dimension from columns, the columns must be in one of the other dimension's tables, but they do not have to be part of the dimension's definition (for example, the source of a level). For more information about member properties, see Creating Member Properties.

To create a virtual dimension based on member properties, use the Dimension Wizard. The wizard allows you to select the member properties that define the virtual dimension. Virtual dimensions based on member properties cannot be created in Dimension Editor. They can be created in Cube Editor only if you start the Dimension Wizard from within Cube Editor. However, after it is created, a virtual dimension can be edited in Dimension Editor (if the virtual dimension is shared) or Cube Editor (if the virtual dimension is private).

To create a virtual dimension based on member properties