The simulate feature shows you which records would be deployed if actually deploying the data set. Because no destination org is involved, the simulation results do not show potential deployment errors or which record handling operation (insert, update, upsert) would be used for each record. 

To simulate a data set deployment from the data set editor:

1. From the Data Set Editor, click Simulate.
2. Here you will be directed to Guided Deployment to select your source and destination.
3. The data set should be preselected.
4. Click Validate at the bottom of the page.
5. Monitor the progress of the simulation on the Deployment History page that appears.
6. Monitor the simulation activity in real-time on the Activity section of the page.

6. On the Deployment History page, the results will appear below the activity.