02010_ch10

02010_ch10 - Database Systems: Design, Implementation, and...

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Database Systems: Design, Implementation, and Management Eighth Edition Chapter 10 Transaction Management and Concurrency Control
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th 2 Objectives In this chapter, you will learn: About database transactions and their properties What concurrency control is and what role it plays in maintaining the database’s integrity What locking methods are and how they work
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th 3 Objectives (continued) In this chapter, you will learn: (continued) How stamping methods are used for concurrency control How optimistic methods are used for concurrency control How database recovery management is used to maintain database integrity
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th 4 What is a Transaction? Logical unit of work that must be either entirely completed or aborted Successful transaction changes database from one consistent state to another One in which all data integrity constraints are satisfied Most real-world database transactions are formed by two or more database requests Equivalent of a single SQL statement in an application program or transaction
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th 5
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th 6 Evaluating Transaction Results Not all transactions update database SQL code represents a transaction because database was accessed Improper or incomplete transactions can have devastating effect on database integrity Some DBMSs provide means by which user can define enforceable constraints Other integrity rules are enforced automatically by the DBMS
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th 7 Figure 9.2
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th 8 Transaction Properties Atomicity All operations of a transaction must be completed Consistency Permanence of database’s consistent state Isolation Data used during transaction cannot be used by second transaction until the first is completed
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th 9 Transaction Properties (continued) Durability Once transactions are committed, they cannot be undone Serializability Concurrent execution of several transactions yields consistent results Multiuser databases subject to multiple concurrent transactions
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th 10 Transaction Management with SQL ANSI has defined standards that govern SQL database transactions Transaction support is provided by two SQL statements: COMMIT and ROLLBACK Transaction sequence must continue until: COMMIT statement is reached ROLLBACK statement is reached End of program is reached Program is abnormally terminated
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th 11 The Transaction Log Transaction log stores: A record for the beginning of transaction For each transaction component: Type of operation being performed (update, delete, insert)
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02010_ch10 - Database Systems: Design, Implementation, and...

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