How to ensure file integrety - best practices

Hi,

I store the data of my app at the moment in a JSON file after every change to the data, because I wan't to make sure that the lastest state is saved.

But for me there are some questions:

1. How can I ensure that my saving operation is not interrupted because the App loose focus?
2. What would be a better approach to reliably sving my data without saving after every change?
3. Should I save always a copy of my data and then delete the old one and rename the new one if the saving could be finished?

Thanks for your advice

Thomas