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14 - Database Recovery(L ect ur e Session-15 Chapt er s 19...

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Database Recovery (Lecture Session-15) Chapters 19 Wed, Feb 24, 2010 1 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS
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Wed, Feb 24, 2010 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS 2 Introduction to Database Recovery Log-based Recovery Deferred modification Immediate Modification Checkpointing Shadow paging Contents
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Wed, Feb 24, 2010 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS 3 Data prior to execution of transaction Exe. of transaction. Data may be in inconsistent state After Execution of the transaction Consistent state Difficulties when failure occur in the process Goes to next consistent state As a result of failure, state of the system will not reflect the state of the real world that the database is supposed to capture. We call that state as inconsistent state . It is important to define transactions such that they preserve consistency.
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Wed, Feb 24, 2010 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS 4 Recovery Techniques If a transaction T performed multiple database modifications, several output operations may be required and a failure may occur after some of these modifications have been made but before all of them are made. In order to ensure atomicity property we must first output the information describing the modifications to stable storage without modifying the database itself. This helps us to output all modifications of a committed transaction. Now we discuss same important recovery techniques.
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Wed, Feb 24, 2010 DLPD, BITS-Pilani.
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