Prerequisites
You have analyzed the fields and structures, as well as the transfer file and your legacy data. In this step you should assign the fields in the legacy system to the fields in transfer file.
There are two ways to assign the fields to each other:
You can use a printout of the interface structure from step 2 to do this.
You can use a commercial tool to assign the fields in the legacy system to the fields in the target structure in the R/3 System and to display them.
As the use of commercial mapping tools is linked to license fees and training costs, it is recommended that you use them if you have to convert several interfaces (> 20) to several legacy systems (> 2).

You must fill all required fields from the online transaction as well as the transfer file. Fields that are not filled contain the NODATA character.
Procedure
Result
You have mapped the fields in your legacy system to the fields in the transfer structure.