Working with a Write-Enabled Dimension
When you create a new member, you must include every attribute in a dimension. You cannot insert a member without specifying a value for the key attribute of the dimension. Therefore, creating members is subject to any constraints (such as non-null key values) that are defined on the dimension table. You should also consider columns optionally specified by dimension properties, such as columns specified in the CustomRollupColumn, CustomRollupPropertiesColumn or the UnaryOperatorColumn dimension properties.