Notes10 - CS245:DatabaseSystem Principles Notes10:MoreTP...

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CS 245 Notes 10 1 CS 245: Database System  Principles Notes 10: More TP Hector Garcia-Molina
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CS 245 Notes 10 2 Sections to Skim: Section 18.8 [18.8] Sections 19.2 19.4, 19.5, 19.6 [none, i.e., read all Ch 19] [In the Second Edition, skip all of Chapter 20, and  Sections 21.5, 21.6, 21.7, 22.2 through 22.7]
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CS 245 Notes 10 3 Chapter 19 [19]   More on transaction      processing Topics: Cascading rollback, recoverable schedule Deadlocks Prevention Detection View serializability Distributed transactions Long transactions (nested,  compensation)
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CS 245 Notes 10 4 Example:          T   T W j (A)   r i (A)   Commit T i Abort T j ……
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CS 245 Notes 10 5 Example:          T   T W j (A)   r i (A)   Commit T i Abort T j ……  Non-Persistent Commit (Bad!)
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CS 245 Notes 10 6 Example:          T   T W j (A)   r i (A)   Commit T i Abort T j ……  Non-Persistent Commit (Bad!) avoided by recoverable schedules
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CS 245 Notes 10 7 Example:          T   T W j (A)   r i (A)   w i (B) Abort T j                                                                [ Commit T i] ……
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CS 245 Notes 10 8 Example:          T   T W j (A)   r i (A)   w i (B) Abort T j                                                                [ Commit T i] ……  Cascading rollback (Bad!)
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CS 245 Notes 10 9 Example:          T   T W j (A)   r i (A)   w i (B) Abort T j                                                                [ Commit T i] ……  Cascading rollback (Bad!) avoided by avoids-cascading- rollback (ACR) schedules
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CS 245 Notes 10 10 Schedule is conflict serializable T j          T i But not recoverable
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CS 245 Notes 10 11 Need to make “final’ decision for each  transaction: commit decision  - system guarantees  transaction will or has completed, no  matter what abort decision  - system guarantees  transaction will or has been rolled back     (has no effect)
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CS 245 Notes 10 12 To model this, two new actions: C i  - transaction T commits A i  - transaction T i  aborts
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Notes 10 13 ...   commit  here?
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This note was uploaded on 02/21/2011 for the course CS 245 taught by Professor Dr.hector during the Winter '02 term at SUNY Buffalo.

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Notes10 - CS245:DatabaseSystem Principles Notes10:MoreTP...

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