We highly recommend doing a backup before beginning this process.
The Bulk value updater is a tool for mass changing records. It updates existing objects: people, addresses, certifications, etc. It does not create new objects, which means that you can use it to modify what's already in VSys, but not to add new people, addresses, and other things.
In most cases, this tool enforces a user's security settings for people and other objects such as hours records, assignments, etc. There are still some VSys Security permissions that the user can bypass and make changes to here.
Changes made here cannot be un-done automatically. If you've accidentally changed everyone's first name to "George", you'll have to either manually re-enter all of the original names, or restore from a backup.
Bulk Value Updater can be run as a Scheduled task.