What are Virtual Dimensions?
Virtual dimensions in TM1/Planning Analytics are an excellent way of adding new analysis capability to a TM1 cube without changing the underlying structure of the cube, or bloating a cube with excessive dimensions. They are “virtual” because they don’t physically exist in a cube. So if you look at a dimension list in either Architect, PAX or PAW, you won’t see them. However, if you look at the hierarchies for a dimension in PAX or PAW, then they are visible.
For a complete explanation of how to create them, please see this post.
What is the Source Information for the Virtual Dimension or Hierarchy
Virtual dimensions, or virtual hierarchies, are created from the contents of an attribute.
So, for example, you might have a list of customers and want to create a virtual hierarchy for Customer State. You would create Customer State as an attribute and then create a virtual dim from that attribute.
Limitations of Virtual Dimensions
You can use virtual dimensions as if they are physical dimensions in Planning Analytics for Excel (PAX), using Explorations or Quick Reports, or in Planning Analytics Workspace (PAW). You cannot use them in TM1 Perspectives or PAX Dynamic Reports or Custom Reports.
You can have as many virtual dims as you like on a physical dimension. You can then intersect the values from one hierarchy with another. For example, building on the example above for Customer State, you might then want to have another virtual dim on the physical Customer dimension for Customer Type. You would add the attribute and hierarchy for Customer Type. Then you would be able to, for example, analyse Customer Type as rows in a crosstab and Customer State as columns – as if they were physical dimensions!
How to Create them?
We have written a full blog post, with code samples, on how you can easily add virtual dimensions. Please see this post how you can add them to any existing TM1 dimension.