Tag: acid properties of transaction

ACID Properties | ACID Properties in DBMS

Database Management System

Transaction in DBMS-

 

Before you go through this article, make sure that you have gone through the previous article on Transactions in DBMS.

 

We have discussed-

  • A transaction is a set of logically related operations.
  • A transaction goes through different states throughout its life cycle.
  • The life cycle of a transaction is-

 

 

In this article, we will discuss ACID properties of a transaction.

 

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.

 

Next Article- Concurrency Problems in DBMS

 

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