One of the last things you want to get from your Commerce site is that the order data is gone. What can be more confused than if your log shows that the cart has been converted into a purchase order, you even got the PO number, but after that, the order disappears? It’s nowhere to be found, even if you look into database. It’s kind of magic, but not the kind of magic you would want to have.
But everything happens for a reason. And actually it’s with a good reason: data consistency.
Episerver Commerce has the concept of TransactionScope. Simply put, it allows two or more database operations to be done as atomic: Either all of them succeed, or all of them will revert back. If a TransactionScope contains 3 operations A, B, C, then even if A, B succeeded, but C is yet to commit, and something goes wrong, then A and B would be reverted.