API_RunImport

What is your question? If you don't supply details and context we are only guessing at what you are ultimately after.

There are several different ways to run mass updates;

1. Grid Edit
2. Search & Replace
3. File Import
4. API_ImportFromCSV
5. API_RunImport
6. Sync Tables
7. Cron Jobs

But it really depends on your use case, and what works best for you.