What Is a Transaction?

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Consider this classic transaction example: A bank needs to transfer a million dollars from bank account A to bank account B. First, the money in A needs to be placed in B. Then, after the transfer has been verified , the money needs to be removed from account A. Obviously, if there is any sort of problem placing the money in account B, you do not want to remove it from account A. Likewise, if the money is placed successfully in account B, you want to ensure that it is removed from account A. All actions need to fail or all actions need to succeed.

If you were coding an application to perform the monetary transactions in the last paragraph, you could do so relatively easily without having to use a transaction by intelligently trapping application errors and maintaining state. However, consider that a transaction isn't limited in size . Imagine keeping track of 500 database changes manually! Also, suppose the server is turned off in the middle of your application's processing. You need to make sure that when the application is brought back online, it knows exactly where it stopped so that it can either reverse all the changes made or attempt to continue where it left off.

Fortunately, because transactions exist, you need not worry about any of these problems. By wrapping your database actions in a transaction, you can help ensure that your data remains correct and consistent. In the next few sections, you'll see how to use database transactions.

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Sams Teach Yourself ADO. NET in 24 Hours
Sams Teach Yourself ADO.NET in 24 Hours
ISBN: 0672323834
EAN: 2147483647
Year: 2002
Pages: 237

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