Magento 2 data patches run once when you install a module or when you upgrade to the latest version. When you are testing some modules then as a Magento developer you may have to run data patches multiple times.
Steps to run existing data patches file in Magento 2
Step 1: Open the “patch_list” table of the website database.
Step 2: delete the entry of your existing patch.
Step 2: run setup:upgrade command to run your patch file.
Here is the our previous blog post Magento 2 Create db_schema_whitelist.json File if you missed it.