Amy’s transactions had an undesirable end result. A transaction is a sequence of server operations that must be carried out atomically (which means that either all operations must be executed or none of them will be executed at all). Amy’s bank operations violated the atomicity property of transactions and caused problems for her. Certainly this is not desirable. It also violated a consistency property that corresponds to the fact that the total money in Amy’s accounts will remain unchanged during a transfer operation. A transaction commits when all of its operations complete successfully and the states are appropriately updated. Otherwise, the transaction aborts, which implies no change will take place and the old state will be retained.