Before using Data Integrity, back up your data. Data Integrity can make bulk changes to data, and reverting changes needs to be done manually. Having a backup is advised.
To back up your data, follow the instructions in Export Backup Data from Salesforce in Salesforce Help. We strongly recommend using the Schedule Export option to set up recurring weekly or monthly backups.
Important Exported backup data is only available for download for 48 hours.
Salesforce emails you when your export data is available, but it's also a good idea to
put a reminder on your calendar.