A transaction is a logical set of updates of persistent data. For example, transferring some amount of money from one account to another is a banking transaction. It is important for transactions to be atomic: Either all of the data fields are updated, or none are. The Java Card RE provides robust support for atomic transactions, so that card data is restored to its original pre-transaction state if the transaction does not complete normally. This mechanism protects against events such as power loss in the middle of a transaction, and against program errors that might cause data corruption should all steps of a transaction not complete normally.