You are treading on extremely thin ice if you do what you claim to want. I advise using the [VACUUM INTO filename](https://sqlite.org/lang_vacuum.html) statement (in "SQL") or the [online backup API](https://sqlite.org/backup.html) to get your copy made, and forget about trying to 2nd guess how things are working under the covers. I would also advise you to consider yourself lucky that your doomed-to-fail (eventually) initial copying attempt failed early. And, going even further, I hope you appreciate that "try it and see what happens" is a perilous approach to writing software. I hope you learn not to do that before ever working on flight software, banking software, any software I use, or nuclear armed missile launch software.