Durability

D.

Durability - Durability means that once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors.

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: 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.

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.

The correct answer is D. Durability.

ACID (Atomicity, Consistency, Isolation, and Durability) is a set of properties that guarantee reliability and consistency in database transactions.

Atomicity ensures that a transaction is treated as a single, indivisible unit of work. Consistency ensures that a transaction brings the database from one valid state to another. Isolation ensures that multiple transactions can operate concurrently without interfering with each other.

Durability is the property that guarantees that once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors. In other words, changes made by a committed transaction are permanent and will survive any subsequent system failures. This is usually accomplished by writing changes to a transaction log or some other form of persistent storage.

Durability is crucial for ensuring the reliability and integrity of a database system. Without durability, a system would be vulnerable to data loss or corruption in the event of a failure. Therefore, database systems often implement various mechanisms to ensure durability, such as write-ahead logging, checkpointing, and backups.