vb.net qr code generator free Understanding Transactions in Visual Basic .NET

Create Data Matrix 2d barcode in Visual Basic .NET Understanding Transactions

CHAPTER
Draw Data Matrix 2d Barcode In Visual Basic .NET
Using Barcode creation for .NET Control to generate, create Data Matrix ECC200 image in .NET framework applications.
www.OnBarcode.com
Decode Data Matrix 2d Barcode In VB.NET
Using Barcode scanner for .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Understanding Transactions
Barcode Creation In VB.NET
Using Barcode creator for .NET framework Control to generate, create Barcode image in VS .NET applications.
www.OnBarcode.com
Creating Linear 1D Barcode In Visual Basic .NET
Using Barcode maker for .NET Control to generate, create Linear Barcode image in Visual Studio .NET applications.
www.OnBarcode.com
For any business, transactions, which may comprise many individual operations and even other transactions, play a key role. Transactions are essential for maintaining data integrity, both for multiple related operations and when multiple users update the database concurrently. This chapter will discuss the concepts related to transactions and how transactions can be used in SQL Server 2005 and VB.NET. In this chapter, we ll cover the following: What is a transaction When to use transactions Understanding ACID properties Transaction design Transaction state Specifying transaction boundaries T-SQL statements allowed in a transaction Local transactions in SQL Server 2005 Distributed transactions in SQL Server 2005 Guidelines to code efficient transactions How to code transactions
UPC - 13 Drawer In VB.NET
Using Barcode maker for VS .NET Control to generate, create GS1 - 13 image in .NET framework applications.
www.OnBarcode.com
Drawing 2D Barcode In VB.NET
Using Barcode creation for VS .NET Control to generate, create 2D Barcode image in .NET framework applications.
www.OnBarcode.com
What Is a Transaction
ECC200 Generation In Visual Basic .NET
Using Barcode drawer for VS .NET Control to generate, create Data Matrix 2d barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Leitcode Encoder In VB.NET
Using Barcode generator for .NET framework Control to generate, create Leitcode image in .NET applications.
www.OnBarcode.com
A transaction is a set of operations performed so all operations are guaranteed to succeed or fail as one unit. A common example of a transaction is the process of transferring money from a checking account to a savings account. This involves two operations: deducting money from the checking account and adding it to the savings account. Both must succeed together and be committed to the accounts, or both must fail together and be rolled back so that the accounts are maintained in a consistent state. Under no circumstances should money be deducted
Printing Data Matrix In .NET
Using Barcode drawer for ASP.NET Control to generate, create DataMatrix image in ASP.NET applications.
www.OnBarcode.com
Create Data Matrix In None
Using Barcode drawer for Online Control to generate, create ECC200 image in Online applications.
www.OnBarcode.com
CHAPTER 8 s UNDERSTANDING TRANSACTIONS
Barcode Scanner In Visual C#
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Generate QR Code In Objective-C
Using Barcode maker for iPhone Control to generate, create QR Code 2d barcode image in iPhone applications.
www.OnBarcode.com
from the checking account but not added to the savings account (or vice versa) at least you would not want this to happen with the transactions occurring with your bank accounts. By using a transaction, both the operations, namely debit and credit, can be guaranteed to succeed or fail together. So both accounts remain in a consistent state all the times.
DataMatrix Reader In Visual Studio .NET
Using Barcode scanner for .NET framework Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Code 128 Code Set A Generator In None
Using Barcode creator for Microsoft Word Control to generate, create Code 128 Code Set C image in Word applications.
www.OnBarcode.com
When to Use Transactions
Code 39 Full ASCII Decoder In Visual Studio .NET
Using Barcode recognizer for VS .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
PDF417 Recognizer In C#
Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
You should use transactions when several operations must succeed or fail as a unit. The following are some frequent scenarios where use of transactions is recommended: In batch processing, where multiple rows must be inserted, updated, or deleted as a single unit Whenever a change to one table requires that other tables be kept consistent When modifying data in two or more databases concurrently In distributed transactions, where data is manipulated in databases on different servers When you use transactions, you place locks on data pending permanent change to the database. No other operations can take place on locked data until the lock is released. You could lock anything from a single row up to the whole database. This is called concurrency, which means how the database handles multiple updates at one time. In the bank example, locks ensure that two separate transactions don t access the same accounts at the same time. If they did, either deposits or withdrawals could be lost.
Generate QR Code In Java
Using Barcode creator for Java Control to generate, create QR Code image in Java applications.
www.OnBarcode.com
PDF417 Scanner In .NET Framework
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
s Note It s important to keep transactions pending for the shortest period of time. A lock stops others from accessing the locked database resource. Too many locks, or locks on frequently accessed resources, can seriously degrade performance.
Generating Linear Barcode In .NET Framework
Using Barcode generation for VS .NET Control to generate, create Linear 1D Barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Recognizing QR-Code In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Understanding ACID Properties
A transaction is characterized by four properties, often referred to as the ACID properties: atomicity, consistency, isolation, and durability.
s Note The term ACID was coined by Andreas Reuter in 1983.
CHAPTER 8 s UNDERSTANDING TRANSACTIONS
Atomicity: A transaction is atomic if it s regarded as a single action rather than a collection of separate operations. So, only when all the separate operations succeed does a transaction succeed and is committed to the database. On the other hand, if a single operation fails during the transaction, everything is considered to have failed and must be undone (rolled back) if it has already taken place. In the case of the order-entry system of the Northwind database, when you enter an order into the Orders and Order Details tables, data will be saved together in both tables, or it won t be saved at all. Consistency: The transaction should leave the database in a consistent state whether or not it completed successfully. The data modified by the transaction must comply with all the constraints placed on the columns in order to maintain data integrity. In the case of Northwind, you can t have rows in the Order Details table without a corresponding row in the Orders table, as this would leave the data in an inconsistent state. Isolation: Every transaction has a well-defined boundary that is, it is isolated from another transaction. One transaction shouldn t affect other transactions running at the same time. Data modifications made by one transaction must be isolated from the data modifications made by all other transactions. A transaction sees data in the state it was in before another concurrent transaction modified it, or it sees the data after the second transaction has completed, but it doesn t see an intermediate state. Durability: Data modifications that occur within a successful transaction are kept permanently within the system regardless of what else occurs. Transaction logs are maintained so that should a failure occur the database can be restored to its original state before the failure. As each transaction is completed, a row is entered in the database transaction log. If you have a major system failure that requires the database to be restored from a backup, you could then use this transaction log to insert (roll forward) any successful transactions that have taken place. Every database server that offers support for transactions enforces these four ACID properties automatically.
Copyright © OnBarcode.com . All rights reserved.