SFDMU Help CenterSource (Working Copy) CSV Files in SFDMU.
When CSV files are set as a data source, SFDMU analyzes and attempts to repair the provided raw source CSV files. After processing, the final versions are stored in a special directory. These processed files become the working copies, which are then used to import data into the target organization.
You can examine these files in the ./source subdirectory to understand how SFDMU processes your CSVs.
Notes:
Each file is appended with the postfix _source, for example, Account_source.csv.
If multiple Object Sets are used, the sources for the first Object Set are placed in the main ./source subdirectory. The sources for subsequent Object Sets, starting from Object Set #2, are stored in their respective directories, for example, ./source/object-set-2/Account_source.csv.