ch17-Introduction to Transaction Processing Concepts and Theory

Ch17-Introduction to Transaction Processing Concepts and Theory

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Slide 17- 1 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe
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Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter 17 Introduction to Transaction Processing Concepts and Theory
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Slide 17- 3 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter Outline 1 Introduction to Transaction Processing 2 Transaction and System Concepts 3 Desirable Properties of Transactions 4 Characterizing Schedules based on Recoverability 5 Characterizing Schedules based on Serializability 6 Transaction Support in SQL
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Slide 17- 4 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe 1 Introduction to Transaction Processing (1) Single-User System : At most one user at a time can use the system. Multiuser System : Many users can access the system concurrently. Concurrency Interleaved processing : Concurrent execution of processes is interleaved in a single CPU Parallel processing : Processes are concurrently executed in multiple CPUs.
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Slide 17- 5 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Introduction to Transaction Processing (2) A Transaction : Logical unit of database processing that includes one or more access operations (read -retrieval, write - insert or update, delete). A transaction (set of operations) may be stand-alone specified in a high level language like SQL submitted interactively, or may be embedded within a program. Transaction boundaries : Begin and End transaction. An application program may contain several transactions separated by the Begin and End transaction boundaries.
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Slide 17- 6 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Introduction to Transaction Processing (3) SIMPLE MODEL OF A DATABASE (for purposes of discussing transactions): A database is a collection of named data items Granularity of data - a field, a record , or a whole disk block (Concepts are independent of granularity) Basic operations are read and write read_item(X ): Reads a database item named X into a program variable. To simplify our notation, we assume that the program variable is also named X. write_item(X ): Writes the value of program variable X into the database item named X.
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Slide 17- 7 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Introduction to Transaction Processing (4) READ AND WRITE OPERATIONS: Basic unit of data transfer from the disk to the computer main memory is one block. In general, a data item (what is read or written) will be the field of some record in the database, although it may be a larger unit such as a record or even a whole block. read_item(X) command includes the following steps: Find the address of the disk block that contains item X. Copy that disk block into a buffer in main memory (if that disk
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This note was uploaded on 02/23/2012 for the course CS 348 taught by Professor Staff during the Fall '08 term at Purdue University-West Lafayette.

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Ch17-Introduction to Transaction Processing Concepts and Theory

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