What property occur when the database is consistent before and after the transaction?
A transaction can be defined as a group of tasks. A single task is the minimum processing unit which cannot be divided further. Show
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. A’s Account Open_Account(A) Old_Balance = A.balance New_Balance = Old_Balance - 500 A.balance = New_Balance Close_Account(A) B’s Account Open_Account(B) Old_Balance = B.balance New_Balance = Old_Balance + 500 B.balance = New_Balance Close_Account(B) ACID PropertiesA 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.
SerializabilityWhen multiple transactions are being executed by the operating system in a multiprogramming environment, there are possibilities that instructions of one transactions are interleaved with some other transaction.
In a multi-transaction environment, serial schedules are considered as a benchmark. The execution sequence of an instruction in a transaction cannot be changed, but two transactions can have their instructions executed in a random fashion. This execution does no harm if two transactions are mutually independent and working on different segments of data; but in case these two transactions are working on the same data, then the results may vary. This ever-varying result may bring the database to an inconsistent state. To resolve this problem, we allow parallel execution of a transaction schedule, if its transactions are either serializable or have some equivalence relation among them. Equivalence SchedulesAn equivalence schedule can be of the following types − Result EquivalenceIf two schedules produce the same result after execution, they are said to be result equivalent. They may yield the same result for some value and different results for another set of values. That's why this equivalence is not generally considered significant. View EquivalenceTwo schedules would be view equivalence if the transactions in both the schedules perform similar actions in a similar manner. For example −
Conflict EquivalenceTwo schedules would be conflicting if they have the following properties −
Two schedules having multiple transactions with conflicting operations are said to be conflict equivalent if and only if −
Note − View equivalent schedules are view serializable and conflict equivalent schedules are conflict serializable. All conflict serializable schedules are view serializable too. States of TransactionsA transaction in a database can be in one of the following states −
What are the properties of a database transaction?In the context of transaction processing, the acronym ACID refers to the four key properties of a transaction: atomicity, consistency, isolation, and durability. All changes to data are performed as if they are a single operation.
What is consistency in database transaction?Consistency in database systems refers to the requirement that any given database transaction must change affected data only in allowed ways. For a database to be consistent, data written to the database must be valid according to all defined rules, including constraints, cascades, triggers, or any combination.
What is consistency property in DBMS?Consistency is a property ensuring that only valid data following all rules and constraints is written in the database. When a transaction results in invalid data, the database reverts to its previous state, which abides by all customary rules and constraints. Consistency is key to maintain data integrity.
Which of the property of transaction will give an assurance of consistent state of database?ACID Properties are used for maintaining the integrity of database during transaction processing. ACID in DBMS stands for Atomicity, Consistency, Isolation, and Durability.
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