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C20.0046: Database Management Systems Lecture #1 - page 12 / 40

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M.P. Johnson, DBMS, Stern/NYU, Sp2004

12

Problems without an DBMS...

1.System crashes:

Q: What is the problem ?

A: George lost his $100

Same problem even if reordered

2.Simultaneous access by many users

George and Dick visit ATMs at same

Lock checking.txt before each use– what is the problem?

Read ‘savings.txt’

Find&update the rec “George.”

Write ‘savings.txt’

Read ‘checking.txt’

Find&update the rec “George”

Write ‘checking.txt’

CRASH !

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