Question

What is AC ID in DBMS? ​

Answer 1

Explanation:

In computer science, ACID (atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee validity even in the event of errors, power failures, etc.

Answer 2

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ACID Properties-

It is important to ensure that the database remains consistent before and after the transaction.

To ensure the consistency of database, certain properties are followed by all the transactions occurring in the system.

These properties are called as ACID Properties of a transaction.

1. Atomicity-

This property ensures that either the transaction occurs completely or it does not occur at all.

In other words, it ensures that no transaction occurs partially.

That is why, it is also referred to as “All or nothing rule“.

It is the responsibility of Transaction Control Manager to ensure atomicity of the transactions.

2. Consistency-

This property ensures that integrity constraints are maintained.

In other words, it ensures that the database remains consistent before and after the transaction.

It is the responsibility of DBMS and application programmer to ensure consistency of the database.

3. Isolation-

This property ensures that multiple transactions can occur simultaneously without causing any inconsistency.

During execution, each transaction feels as if it is getting executed alone in the system.

A transaction does not realize that there are other transactions as well getting executed parallely.

Changes made by a transaction becomes visible to other transactions only after they are written in the memory.

The resultant state of the system after executing all the transactions is same as the state that would be achieved if the transactions were executed serially one after the other.

It is the responsibility of concurrency control manager to ensure isolation for all the transactions.

4. Durability-

This property ensures that all the changes made by a transaction after its successful execution are written successfully to the disk.

It also ensures that these changes exist permanently and are never lost even if there occurs a failure of any kind.

It is the responsibility of recovery manager to ensure durability in the database.