Database Reference
In-Depth Information
9
Managing Multiuser Databases
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To understand the need for and importance of database
administration
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To understand the need for concurrency control, security,
and backup and recovery
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To learn about typical problems that can occur when
multiple users process a database concurrently
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To understand the use of locking and the problem
of deadlock
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To learn the difference between optimistic and
pessimistic locking
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To know the meaning of an ACID transaction
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To learn the four 1992 ANSI standard isolation levels
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To understand the need for security and specific tasks
for improving database security
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To know the difference between recovery via
reprocessing and recovery via rollback/rollforward
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To understand the nature of the tasks required
for recovery using rollback/rollforward
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To know basic administrative and managerial
DBA functions
Although multiuser databases
offer great
value to the organizations that create and use
them, they also pose difficult problems for those same
organizations. For one, multiuser databases are complicated
to design and develop because they support many overlapping user views.
Additionally, as discussed in the last chapter, requirements change over
time, and those changes necessitate other changes to the database structure.
Such structural changes must be carefully planned and controlled so that a
change made for one group does not cause problems for another. In addition,
when users process a database concurrently, special controls are needed to
ensure that the actions of one user do not inappropriately influence the results
for another. This topic is both important and complicated, as you will see.
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