Almost any relational database system provides the facility for database transactions. Database transactions are a set of commands that either all fail or all succeed, as a group. ADO.NET provides a set of objects used to create and work with transactions, which will be discussed in this lesson. Other articles by Jason Lefebvre. |
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See all Sams Teach Yourself on InformIT Programming Tutorials. In the preceding hour, you saw how to use SQL and OLE DB connection pooling
in your applications to increase your application's responsiveness and
decrease the amount of system resources used. In this hour, you're going
to see how database transactions can help maintain the integrity of your database.
A transaction is a set of actions that are executed as a group, with all actions
succeeding or all actions failing.
In this hour, you'll see how to
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Initiate a database transaction using ADO.NET
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Roll back changes made to a database
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Save changes made while using a transaction
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Perform a database transaction in a stored procedure
What Is a Transaction?
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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