[maskros]

To backup you should use the `vacuum into` statement. That can be safely run from another process, as it takes a read lock and doesn't block writers when using the WAL mode.

When backing up a SQLite database that is in running use, you should never use `.backup`. That command will restart the backup from scratch every time the database is written to, so if you're backing up a big database with a lot of periodic writes the backup process may never complete.

You can sometimes use the C backup API from the same process that is writing to the database, since the C backup API is aware of writes _from the same process_. It will still have to restart the backup procedure if writes from another process interfere.

[anze3db]

Great point. I thought that `vacuum into` blocks writes, but it's only `vacuum` that blocks! I've updated the blog post, thanks!