Transaction Concepts

Unit: III: Transactions

Syllabus

Transaction Concepts - ACID Properties - Schedules - Serializability - Transaction support in SQL - Need for Concurrency - Concurrency control - Two Phase Locking- Timestamp - Multiversion Validation and Snapshot isolation - Multiple Granularity locking - Deadlock Handling - Recovery Concepts - Recovery based on deferred and immediate update - Shadow paging - ARIES Algorithm.

Part I: Introduction to Transactions

Transaction Concepts                                         

AU: Dec.-14, Marks 4

Definition: A transaction can be defined as a group of tasks that form a single logical unit. 

For example - Suppose we want to withdraw 100 from an account then we will follow following operations:

1) Check account balance

2) If sufficient balance is present request for withdrawal.

3) Get the money

4) Calculate Balance = Balance -100

5) Update account with new balance.

The above mentioned four steps denote one transaction.

In a database, each transaction should maintain ACID property to meet the consistency and integrity of the database.

Review Question

1. Write a short note on - Transaction Concept.   AU: Dec- 14,Mark 4