Database Reference
In-Depth Information
CHAPTER 15
DATA INTEGRITY
CHAPTER OBJECTIVES
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Learn what data integrity is and why it is extremely important
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Note the nature and significance of a database transaction
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Study the meaning of ACID properties of transactions and appreciate why a
database system must preserve these
•
Understand concurrent transactions and the types of problems they could
cause
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Discuss serializability and recoverability of transactions
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Examine various methods of concurrency control
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Classify the potential types of failures in a database environment and review
recovery concepts
•
Survey logging and log-based recovery techniques
•
Inspect shadow paging and its role as a recovery method
Take the case of a banking database system. Consider this scenario. Assume that
one of the bank's customers wants to transfer $50,000 from his or her savings
account to the his or her checking account to cover a check issued for an important
deal. The check bounces, and on investigation the bank discovers that although
$50,000 was deducted from the customer's savings account the amount was not
added to the checking account. The bank loses an important but irate customer.
Why? What has happened?
That database transaction transferring the amount from savings to checking
accounts did not leave the database in a consistent state. Only one part of the trans-
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