Answer
It can be run while the environment stays online, but two things are worth understanding first. The resulting backup only reflects data as of the moment the backup process started — any transactions made in the application while the backup itself is still running won't be captured in that backup, regardless of when the backup actually finishes. And running it online requires the application server to have enough spare CPU/memory headroom, since a resource-intensive backup running in the background can cause a noticeable performance drop for other users actively using the application at the same time if the server is already close to its resource limits — plan the timing and server capacity accordingly rather than assuming an online backup is always risk-free.