The Mix Ref serves as a unique identifier for each Mix in the data base.
When you are adding a record to the Mix Table you must enter a Mix Ref (max. 12 characters), which does not duplicate a Mix Ref already in the data base. Since it may be referred to in the Batches Table, it is advisable to select a descriptive Mix Ref which will be recognisable.
An existing Mix Ref cannot be changed.