Question 1: ACID stands for: a) Atomicity, consistency, isolation, and durabilit

Question

Question 1: ACID stands for: a) Atomicity, consistency, isolation, and durability b) Atomicity, command, integrity, and data cAtomicity, control, integrated, and direct d) None of these i. i. Which of the following is not an ACID property? a) Atomicity b) Concurrency c) Isolation d) Durability e) Serializability. ii. Identify the correct ACID property for the following statements: a) The means that data used during the execution of a transaction cannot be used by a second transaction until the first one is completed. b) "alor-none"property c) One of the requirements of transaction management is that after the successful execution of the transaction, the new values in the database must persist even if there is a system failure. d) Ensures that once transaction changes are done, they cannot be undone or lost, even in the event of a system failure.

Explanation / Answer

1) ACID stands for Atomicity, Consistency, Isolation, Durability.

2)Concurrency control ensures that correct results for concurrent operations are generated for getting those results as quickly as possible while a system which maintains transaction isolation, enforces serializability.

Atomicity ensures whether the transaction is atomic or not. It requires that each transaction is "all or none" that is if one part of the transaction fails, then the entire transaction fails, and the database state is left unchanged.

Isolation property demands that the data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.Providing isolation is the main goal of concurrency control. Depending on the concurrency control method the effects of an incomplete transaction might not even be visible to another transaction.

Durability ensures that once transaction changes are done they cannot be undone or lost even in the event of a system failure.It makes the developer know that the transaction is a permanent part of the system. There are safeguards that helps in preventing the loss of information, even in the case of system failure( point (c) in the above question says this only). A non-volatile memory should be used to keep a record of the transaction to fight against power loss.

Consistency property ensures that the end of any transaction the system must be in a valid state. If the transaction is successfully completed, then all changes to the system will be properly made, and the system will be in a valid state. If any error occurs in a transaction, then the system will return to its earlier state.

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