What are the key characteristics of transaction cost economies?

Answer 1

• Atomicity. A transaction must be an atomic unit of work (either all of its data modifications are performed, or none of them is performed).
• Consistency. When completed, a transaction must leave all data in a consistent state. In a relational database, all rules must be applied to the transaction's modifications in order to maintain all data integrity. All internal data structures, such as B-tree indexes or doubly linked lists, must be correct at the end of the transaction.
• Isolation. Modifications made by concurrent transactions must be isolated from the modifications made by any other concurrent transactions. A transaction either sees data in the state it was in before another concurrent transaction modified it or it sees the data after the second transaction has completed, but it does not see an intermediate state. This situation is referred to as serializability, because it results in the capability to reload the starting data and replay a series of transactions in order to end up with the data in the same state it was in after the original transactions were performed.
• Durability. After a transaction has completed, its effects are permanently in place in the system. The modifications persist even in the event of a system failure.