A virtual dimension is a logical dimension based on a property of a level in a physical dimension. This property is called a “member property” and must be created before the virtual dimension. For more information, see Member Properties.
Virtual dimensions enable end users to analyze cube data based on the member properties of dimension level members in a cube. For example, suppose the Store Name level of the Store dimension has a member property Store Sqft that identifies the area of the store in square feet. You can then create a virtual dimension named Store Size in SqFt using the Store Sqft member property. This virtual dimension can be added to any cube that also contains the Store dimension. End users can use this virtual dimension just like any other dimension.
Note You can add a virtual dimension to a cube only if the dimension that supplies its member property is also included in the cube.
Adding a virtual dimension to a cube does not increase the cube’s size because, unlike an ordinary dimension, a virtual dimension’s aggregation data is not stored in the cube. Virtual dimensions do not affect cube processing time because they are calculated in memory when needed. Queries that use virtual dimensions, however, can be significantly slower than queries that use ordinary dimensions.
Microsoft® SQL Server™ OLAP Services provides the Virtual Dimension wizard for easy creation of virtual dimensions.
For more information about virtual dimensions, see Creating Virtual Dimensions.