Cube Dimensionality

A cube is defined by a set of dimensions. A cube can refer to a level that is not the lowest level in a dimension.

For cubes that use a pure relational implementation, you can reuse the same dimension multiple times with the help of dimension roles. For more information on dimension roles, see "Dimension Roles".

Before you validate a cube, ensure that all the dimensions that the cube references are valid.

To define a dimension reference, specify the following:

• The dimension and the level within the dimension to which the cube refers.

  For a cube that uses a relational implementation, you can refer to intermediate levels in a dimension. However, for cubes that use a MOLAP implementation, you can only reference the lowest level in the dimension. OWB supports a reference to the non surrogate identifier of a level, for example, the business keys.

• For dimensions that use a relational or ROLAP implementation, a dimension role for each dimension to indicate what role the dimension reference is performing in the cube. Specifying the dimension role is optional.

When you define a MOLAP cube, the order in which you define the dimension references is important. The physical ordering of dimensions on disk is the same as the order in which you define the dimension references. The physical ordering is tightly coupled with the sparsity definition. Define the dimension references in the order of most dense to least dense. Time is usually a dense dimension, and listing it first expedites data loading and time-based analysis. For more information on defining dimension references, see "Dimensions Page" or "Dimensions Tab" in Warehouse Builder Online Help. For more information on sparsity, see Advanced Dialog Box" in Warehouse Builder Online Help.

Default Aggregation Method 

You can define aggregations that should be performed on the cube. For ROLAP cubes, you can only define a single aggregation method for the cube. For MOLAP cubes, you can define a different aggregation method for each dimension of each measure. OWB enables you to use the same aggregation function for all the cube measures or specify different aggregate functions for each measure.

OWB supports the following default aggregation methods: SUM, SSUM (scaled SUM), AVERAGE, HAVERAGE (hierarchical average), MAX, MIN, FIRST, LAST, AND, OR, HIERARCHICAL_FIRST and HIERARCHICAL_LAST. If you do not want to perform aggregation, select NOAGG. The methods AND and OR are not applicable for cubes that use a multidimensional implementation.