Which of the following ACID property ensures that transaction will bring the database from one valid state to another?
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A. B. C. D.B.
Consistency - The consistency property ensures that any transaction will bring the database from one valid state to another.
Any data written to the database must be valid according to all defined rules, including but not limited to constraints, cascades, triggers, and any combination thereof.
This does not guarantee correctness of the transaction in all ways the application programmer might have wanted (that is the responsibility of application-level code) but merely that any programming errors do not violate any defined rules.
For CISA exam you should know below information about ACID properties in DBMS: Atomicity - Atomicity requires that each transaction is "all or nothing": if one part of the transaction fails, the entire transaction fails, and the database state is left unchanged.
An atomic system must guarantee atomicity in each and every situation, including power failures, errors, and crashes.
To the outside world, a committed transaction appears (by its effects on the database) to be indivisible ("atomic"), and an aborted transaction does not happen.
Consistency - The consistency property ensures that any transaction will bring the database from one valid state to another.
Any data written to the database must be valid according to all defined rules, including but not limited to constraints, cascades, triggers, and any combination thereof.
This does not guarantee correctness of the transaction in all ways the application programmer might have wanted (that is the responsibility of application-level code) but merely that any programming errors do not violate any defined rules.
Isolation - The isolation property ensures that the concurrent execution of transactions results in a system state that would be obtained if transactions were executed serially, i.e.
one after the other.
Providing isolation is the main goal of concurrency control.
Depending on concurrency control method, the effects of an incomplete transaction might not even be visible to another transaction.[citation needed] Durability - Durability means that once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors.
In a relational database, for instance, once a group of SQL statements execute, the results need to be stored permanently (even if the database crashes immediately thereafter)
To defend against power loss, transactions (or their effects) must be recorded in a non-volatile memory.
The following were incorrect answers: Atomicity - Atomicity requires that each transaction is "all or nothing": if one part of the transaction fails, the entire transaction fails, and the database state is left unchanged.
Isolation - The isolation property ensures that the concurrent execution of transactions results in a system state that would be obtained if transactions were executed serially, i.e.
one after the other.
Durability - Durability means that once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors.
The ACID (Atomicity, Consistency, Isolation, and Durability) properties are the four essential characteristics that ensure the reliability of transactions in a database management system. Each property has a unique function that guarantees the integrity and consistency of data in a transactional environment.
Of the four ACID properties, the one that ensures that a transaction will bring the database from one valid state to another is consistency.
Consistency ensures that a transaction brings the database from one valid state to another. In other words, it ensures that the transaction does not violate any integrity constraints, such as referential integrity or domain constraints, and that the data remains consistent before and after the transaction. If a transaction violates any constraints, the transaction will not be committed, and the database will remain in its previous state.
Atomicity guarantees that a transaction is treated as a single, indivisible unit of work, which means that either all the changes made by the transaction are applied to the database, or none of them are applied. If the transaction fails at any point, all changes made by the transaction are rolled back to their original state.
Isolation ensures that multiple transactions can occur concurrently without interfering with each other. Each transaction is isolated from other transactions until it is completed, ensuring that the database remains consistent.
Durability ensures that once a transaction is committed, its changes are permanent and will survive any subsequent failures or errors, such as power outages, system crashes, or network failures.
Therefore, the ACID property that ensures that a transaction will bring the database from one valid state to another is Consistency.