As a System Administrator, you will need to determine which data importing tool is most suitable for your use case. This article explains the differences between using Data Import Wizard and Data Loader.
Importing your data into Rethink is a big task, so hats off to you if you are up for the challenge! We've broken it down for you to make the process as easy as possible. We do highly recommend working with one of our established partners to migrate your data, but if you're ready to pull up your sleeves and accomplish this task yourself, we're here to guide you through the process.
When importing your data, you'll find two options available in Setup:
Data Import Wizard: A simple, easy to follow in-browser tool for uploads containing up to 50,000 records.
Data Loader: A more technical data upload application for data sets of any size.
Data Import Wizard
This is a great tool for smaller data uploads. You can upload data to both Standard and Custom Objects in Rethink, and it's available in both Salesforce Classic (excluding some orgs) and Lightning Experience. Data Import Wizard is best for detecting duplicates and avoiding the same records being imported to Rethink multiple times, so you won't have to worry about deduplicating your data after the fact.
Data Loader
This tool is an application that you'll need to download to your computer prior to starting your upload. Data Loader is great for larger data uploads of 50,000 to 5 million records. If you wish to schedule regular uploads with large amounts of data, you can achieve this with Data Loader. Also available in Salesforce Classic (excluding some orgs) and Lightning Experience, this tool is slightly more technical than Data Upload Wizard.