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Explain log based recovery
written 7.8 years ago by | • modified 7.8 years ago |
Mumbai University > Information Technology > Sem 3 > Database Management System
Marks: 10 M
Year: Dec 2013
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written 7.8 years ago by | • modified 7.8 years ago |
Mumbai University > Information Technology > Sem 3 > Database Management System
Marks: 10 M
Year: Dec 2013
written 7.8 years ago by |
Log based recovery works as follows:
<Tn, Start>
<Tn, X, V1, V2>
It reads Tn has changed the value of X, from V1 to V2.
When transaction finishes, it logs:
<Tn,commit>
Database can be modified using two approaches:
Deferred database modification: All logs are written on to the stable storage and database is updated when transaction commits.
Immediate database modification: Each log follows an actual database modification. That is, database is modified immediately after every operation.