INTRODUCTION TO TRANSACTION
A transaction can be defined as a group of tasks. A single task is the minimum processing unit which cannot be divided further.
Let’s take an example of a simple transaction. Suppose a bank employee transfers Rs 500 from A’s account to B’s account. This very simple and small transaction involves several low-level tasks.
ACID Properties
A transaction is a very small unit of a program and it may contain several lowlevel tasks. A transaction in a database system must maintain Atomicity, Consistency, Isolation, and Durability − commonly known as ACID properties − in order to ensure accuracy, completeness, and data integrity.
1) Atomicity: This property states that a transaction must be treated as an atomic unit, that is, either all of its operations are executed or none. There must be no state in a database where a transaction is left partially completed. States should be defined either before the execution of the transaction or after the execution/abortion/failure of the transaction.
2) Consistency: The database must remain in a consistent state after any transaction. No transaction should have any adverse effect on the data residing in the database. If the database was in a consistent state before the execution of a transaction, it must remain consistent after the execution of the transaction as well.
3) Isolation: In a database system where more than one transaction are being executed simultaneously and in parallel, the property of isolation states that all the transactions will be carried out and executed as if it is the only transaction in the system. No transaction will affect the existence of any other transaction.
4) Durability: The database should be durable enough to hold all its latest updates even if the system fails or restarts. If a transaction updates a chunk of data in a database and commits, then the database will hold the modified data. If a transaction commits but the system fails before the data could be written on to the disk, then that data will be updated once the system springs back into action.
More topics from DBMS to read:
DATABASE MANAGEMENT SYSTEM
EasyExamNotes.com covered following topics in DBMS.
- Introduction to Database
- Introduction to DBMS
- History of DBMS
- Disadvantages of file system data managemen
- Database system application
- Advantages and disadvantages of DBMS
- DML, DDL and DCL
- Domains
- Introduction to data models
- Entities and Attributes
- Relationship among entities
- Tuples
- Attributes
- Relation
- Characterstic of Relation
- Keys
- Relational Database
- Schemas
- Integrity Constraints
- Referential Integrity
- Numerical One
- Normalization
- Functional dependency
- Transaction processing concepts
- Serializability
- Conflict Serializability
- Schedule
- Schedule recoverability
- Schedule example
- OODBMS vs RDBMS
- RDBMS
- SQL join
- Defining primary keys, foreign keys in a table
- CHECK constraints
- SQL functions: SUM(), AVG(), MAX(), MIN(), COUNT().
- Block, Extent, Segment
- Oracle
- Oracle Background processes
- Trigger
- Create Trigger
- Oracle cursor
- Oracle cursor types
- Create Explicit cursor
- Introduction to Transaction
- Introduction to Concurrency Control
- Data Mining and Data Warehousing
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