Design Exploration > Working with Design Exploration > About the Pre-modified Models
  
About the Pre-modified Models
A pre-modified checkpoint is created automatically when you start a new Design Exploration session. When you set the des_exp_create_backups configuration option to yes or set the environment option to back up models in session, the premodified checkpoint contains information of the unmodified versions of the following models:
All models open when you start a Design Exploration session
All models you open while in the Design Exploration session
When you do not back up models in session or when you set the des_exp_create_backups configuration option to no, the system stores pointers to the files but does not create backups.