If your CSV file contains some invalid IDs, the following outcomes occur:
- Files are attached successfully to the valid IDs' corresponding records.
Please ensure that all IDs in your CSV file are valid to prevent any errors during the file attachment process.
PS: View Mass File Upload, Salesforce file upload app on Salesforce AppExchange: https://appexchange.salesforce.com/appxListingDetail?listingId=82cf236b-1ee8-4ea7-aebf-fd0c89fb93bd