SQLite uses advisory locks but the `cp` command won't adhere to those so you can get a copy that contains only some of the writes from a transaction. If you're lucky, you just get some wonky data. If you're unlucky, you can get a corrupted copy.

Transactions are only atomic from the perspective of other transactions. Other processes or commands on the system can see partial state. This applies to both the rollback journal & the WAL modes.

File copies are also covered in their "How to Corrupt a SQLite Database File" web page[1].

[1]: https://www.sqlite.org/howtocorrupt.html#_backup_or_restore_...