When you drag and drop a column from a bodily desk that is not currently getting used in your logical desk in BMM layer, the bodily desk containing such column gets brought as a brand new Logical Table Source (LTS).
When in BMM layer, you operate more than one table as source desk, it is called a couple of logical desk sources. You may have a Fact desk as more than one logical desk sources when it uses one of a kind bodily tables as source.
Multiple LTS are used to transform Snowflakes schema to Star schemas in BMM layer.
Let us say you have dimensions − Dim_Emp and Dim_Dept and one truth table FCT_Attendance in the Physical layer.
Here your Dim_Emp is normalized to Dim_Dept to implement Snowflakes schema. So for your Physical diagram, it would be like this −
When we move those table to the BMM layer, we are able to create a single measurement desk Dim_Employee with 2 logical sources similar to Dim_Emp and Dim_Dept. In your BMM diagram −
This is one approach in which you can use idea of multiple LTS in BMM layer.
When you operate multiple bodily tables as sources, you enlarge table sources in BMM diagram. It indicates all multiple LTS from where it's far selecting up the facts in BMM layer.
To see desk mapping in BMM layer, extend the sources underneath logical desk in BMM layer. It will open Logical table source mapping speak container. You can test all tables that are mapped to offer data in logical table.