A transaction can be defined as a sequence of operations performed together as a single logical unit of work. A single logical unit of work which evolves one or more database access operations must possess the four properties called ACID (Atomicity, Consistency, isolation, durability).
Atomicity states that either all the data modifications are performed or none of them are performed.
Consistency is a state in which all the data in a consistent state after a transaction is completed successfully.
Isolation states that any data modification made by a transaction must be isolated from the modifications made by any other concurrent transactions. In other words, a transaction either accesses data in the state it was on, before another concurrent transaction modified it or it access the data after the second transaction has been completed. There is no scope for the transaction to see an intermediate state.
Durability states that any changes in data by a completed transaction remain permanently in effect in the system. Hence any change in data due to a completed transaction persists even in the event of a system failure.
No comments:
Post a Comment