CHAPTER 8Transactions

Tansactions are one of the features that set a database apart from a file system. In a file system, if you are in the middle of writing a file and the operating system crashes, this file is likely to be corrupted. It is true there are "journaled" file systems and the like, which may be able to recover your file to some point in time. However, if you need to keep two files synchronized, such as system won't help you there—if you update one file, and the system fails before you finish updating the second, then you will have out-of-sync files.

This is the main purpose of transactions in the database; they take the database from one consistent state to the next. That is their job. When you commit work in the database, you are ...

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