az sql db copy - performance characteristics: what is the impact on source db?

I just wanted to enquire, because there is [nothing in the documentation](https://docs.microsoft.com/en-us/cli/azure/sql/db?view=azure-cli-latest#az-sql-db-copy), but what are the performance or uptime considerations when executing `az sql db copy` ?

Like, what is it actually doing behind the scenes?

I ask because for some reason, when managing via `az sql db export` and `az sql db import` of bacpacs via storage, it seems to take a very long time, say about 1 to 1.5hrs, even if all in same region, for a large (say 60gb) database. In contrast, `az sql db copy` seems to do the same without even breaking a sweat, sometimes completing in about 2 to 3 minutes, even between servers?

Why? How does it achieve this speed? And what happens to the source DB during the copy? Is it still available? Is there some kind of cost/pricing dimension involved?

Can bacpacs be processed with similar efficiency?

TL;DR: I want to know if `az sql db copy` is safe to use with production databases as the source!

Thanks!