SAP Lumira 1.29.3 : to merge data

Hello,

I use SAP Lumira 1.29.3

I need your help to merge data between 2 files

In each file, I create a same variable (uppercase(dimension))

When I must to merge data, SAP Lumira refuses because "search columns that are selectionned are not a unique key"

This 2 columns are my only unique key

What's the solution ?

Have you an idea to resolve this problem ?

Thanks for your help

Carole