4. Atomic Transaction

A transaction is a series of instructions, operations or actions that perform a single logical function. All the instructions of a particular transaction has to be completed in order to complete it successfully. Atomic transactions refers to a transaction in which either all instructions are executed successfully or none of them. If the execution stops in the middle, due to some error, then all the previously performed actions of that transactions are rolled back or undone. Atomic transactions are needed ensure consistent data access.
    A transaction may be committed, if all its actions are successfully completed otherwise it is aborted, in which case all the mofifications which it has done are rolled back to undo them. The property of storage devices also plays an important role in implementing atomic transactions.

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