Saturday, September 13, 2014

Transaction : Explain the characteristics of a transaction server for example Atomicity, Consistency, Isolation, Durability?

Characteristics of a transaction:-
Atomicity
This characteristic of a transaction means that a transaction is performed completely not performed at all. I.e. all the tasks in a transaction are completed or none are completed. E.g. transferring money from one account to another involves credit from one account and debit to another.
Consistency
This characteristic means that the database should be consistent before and after the transaction. For a successful transaction database can move from one state to another. Both the states should abide by the same rules. For an unsuccessful transaction, if the transaction fails to abide by the rule and leads to an inconsistent state, the transaction should be rolled back.
Isolation
A transaction should be isolated. This means that that no other operation should be allowed to access or see the intermediate state data.
Durability
A transaction on completion must persist. It should withstand system failures and should not be undone.


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