Databases Reference
In-Depth Information
7. Explain how the combination of views and the
SQL GRANT command limits access to a relational
database.
8. What is data encryption and why is it important to
data security?
9. In your own words, describe how Secure Socket
Layer (SSL) technology works.
10. In your own words, describe how a proxy server
firewall works.
11. Explain why backup and recovery is important.
12. What is a journal or log? How is one created?
13. Describe the two different problems that forward
recovery and backward recovery are designed to
handle. Do mirrored databases address one of these
two problems or yet a third one? Explain.
14. In your own words, describe how forward recovery
works.
15. In your own words, describe how backward recovery
works.
16. What is disaster recovery? Can the techniques for
backup and recovery be used for disaster recovery?
17. Explain why concurrency control is important.
18. What is the lost-update problem?
19. What are locks and how are they used to prevent the
lost-update problem?
20. What is deadlock and how can it occur?
EXERCISES
order is sent from the touch-screen terminal to the
computer only after all of it has been entered.
At 8:00 PM there are 10 servings of salmon, 15
servings of flounder, and eight orders of trout left in
the kitchen. At 8:03 PM, waiter Frank starts entering
an order that includes five servings of salmon, six
of flounder, and four of trout. At the same time,
on another touch-screen terminal, waitress Mary
starts entering an order that includes one serving
of salmon, three of flounder, and two of trout. At
8:05 PM, before the other two have finished entering
their orders, waitress Tina starts entering an order
that includes six servings of salmon, one of flounder,
and five of trout. Frank finishes entering his order
at 8:06 PM, Mary finishes at 8:07 PM, and Tina
finishes at 8:09 PM.
a. What would the result of all of this be in the
absence of locks?
b. What
1. A large bank has a headquarters location plus
several branches in each city in a particular region
of the country. As transactions are conducted at
each branch, they are processed online against a
relational database at headquarters. You have been
hired as the bank's Director of Data Security. Design
a comprehensive set of data security measures to
protect the bank's data.
2. The bank in Exercise 1, which it totally dependent
on its relational database, must be able to keep
running in the event of the failure of any one table
on one disk drive, in the event of a major disaster
to its headquarters computer, or in the event of any
catastrophe between these two extremes. Describe
the range of techniques and technologies that you
would implement to enable the bank to recover from
this wide range of failures.
3. The Tasty Seafood Restaurant is a large restaurant
that specializes in fresh fish and seafood. Because
its reputation for freshness is important to Tasty,
it brings in a certain amount of each type of fish
daily and, while trying to satisfy all of its customers,
would rather run out of a type of fish than carry it
over to the next day. After taking a table's order, a
waiter enters the order into a touch-screen terminal
that is connected to a computer in the kitchen. The
would
the
result
be
with
a
locking
mechanism in place?
c. What would happen if versioning was in use?
4. Construct examples of the lost update problem, the
use of locks, deadlock, and versioning for the case
of a joint bank account (i.e. two people with access
to the same bank account).
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