"SafeFileSave"

"SafeFileSave" is an option for notebooks that determines if Mathematica should take any special precautions before saving a notebook.

With the default setting "SafeFileSave" Prescan, Mathematica estimates the number of bytes in the notebook and checks if adequate disk space is available before saving it. In case the disk space is not enough, you will get an error message.

With the setting "SafeFileSave" TempFile, Mathematica creates and saves a separate copy of the file instead of overwriting the existing copy. This ensures that if you run out of disk space, the last saved version of the file is still available to you. Once the new copy is successfully saved, the previous copy is deleted.

The TempFile setting is relevant for multiple-user platforms like Unix and Windows NT. On such platforms, a file save operation may fail even with adequate disk space on the machine, because the user's disk quota is exceeded

With the setting "SafeFileSave" None, Mathematica does not take any special precautions before saving a notebook. Use this setting if you are sure you have adequate disk space for your files.