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Please Get A Copy of the 6th Edition of Database Systems Concepts
by Silberschatz, Korth, & Sudarshan
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3. WHY DATABSES? 7 Traditional Programming Limitations That Encouraged Database Design Banking Application

4. Problem #1 : Data Redundancy
Duplication of Data!
In Too many files
Too many programs
Maintenance Difficult
Banking Application Example
Jane is an employee of the bank
She is on the administrative team for the bank
She is in charge of the loan department a the bank
She has a checking account at the bank
She has a savings account at the bank!
Information about Jane appears in many files

5. Problem #2 : Data Inconsistency
All those many copies of data are not the same
Banking Application Example
Jane is an employee of the bank
She is on the administrative team for the bank
She is in charge of the loan department a the bank
She has a checking account at the bank
She has a savings account at the bank!
Information about Jane appears in many files
She decides to get married & chooses to take her husbands last name & is moving to his house!
In how many files must her name be changed?
In how many files must her address be changed?

6. Problem #3 : Difficulty Accessing Data
Jane’s Office has just repossessed their first Porsche
She decides to try to make a good offer to one of her existing bank customers.
She Needs a List -> Name, Home Phone, Work Phone
Male
16 – 25
Salary $40,000 +
No Car Loan in 2 years!
The information Jane needs can be collected from a single file.
The current software has No Option to produce such a customized list; the program staff will have to write a custom program for this.
They are busy
Will take several days
Jane waits:

7. Problem #3 : Difficulty Accessing Data (cont.)
Jane’s gets the list  Problem
Insurance Problem? Jane Realizes:
This car costs these young folks $1,200 a month to insure.
The buyer will now have to make $48,000 a year to pay the expected expenses!
She returns to the programming staff needing a list -> Name, Home Phone, Work Phone
Male
16 – 35
Salary $48,000 +
No Car Loan in 2 years!
Jane waits:

8. Problem #4 : Data Isolation
Jane’s Office has just repossessed their first Home
She decides to try to make a good offer to a young married couple from her existing bank customers.
She Needs a List -> Name, Home Phone, Work Phone
No existing home
Combined Salary $120,000
No Car Loan in 1 years!
The information Jane needs has to be collected from multiple files that are in different file formats – more difficult than the Porsche request.
The current software has No Option to produce such a customized list; the program staff will have to write a custom program for this.
They are busy
Will take several days
Jane waits:

9. Problem # 5 : Concurrent Access Anomalies Problems
Multiple users must be able to update the system simultaneously.
Teller
Auditor
Loan Dept.
Drive Through
Check Processing

10. Problem # 5 : Concurrent Access
Anomalies Problems
Multiple users must be able to update the system simultaneously.
Rita & Ken checking  $3,000
Simultaneously, Rita is withdrawing $500 from checking at teller window inside.
Simultaneously, Ken is depositing $50 into checking at the drive through.

11. Problem # 5 : Concurrent Access Anomalies Problems
Multiple users must be able to update the system simultaneously.
Rita & Ken currently have $3,000 in their checking account.
Suppose the Software at the teller windows starts to process Rita’s Transaction:
$ 3,000 - $500 = $2,500
Suppose at the same time, the Software at the drive through window starts to process Ken‘s Transaction:
$ 3,000 + $50 = $3,050
Can You See The Potential Problem?

12. Problem # 5 : Concurrent Access Anomalies Problems
Apply Rita’s Transaction First? – 1A –
Multiple users must be able to update the system simultaneously.
Rita & Ken checking  $3, $2,500
Suppose the Software at the teller windows starts to process Rita’s Transaction:
$ 3,000 - $500 = $2,500
Suppose at the same time, the Software at the drive through window starts to process Ken‘s Transaction:
$ 3,000 + $50 = $3,050

13. Problem # 5 : Concurrent Access Anomalies Problems
Then Apply Ken’s Transaction Second? – 1B –
Multiple users must be able to update the system simultaneously.
Rita & Ken checking  $3, $2, $3,050
Suppose the Software at the teller windows starts to process Rita’s Transaction:
$ 3,000 - $500 = $2,500
Suppose at the same time, the Software at the drive through window starts to process Ken‘s Transaction:
$ 3,000 + $50 = $3,050
Wrong Answer!

14. Problem # 5 : Concurrent Access Anomalies Problems
Then Apply Ken’s Transaction First? – 2A –
Multiple users must be able to update the system simultaneously.
Rita & Ken checking  $3, $3,050
Suppose the Software at the teller windows starts to process Rita’s Transaction:
$ 3,000 - $500 = $2,500
Suppose at the same time, the Software at the drive through window starts to process Ken‘s Transaction:
$ 3,000 + $50 = $3,050
Wrong Answer!

15. Problem # 5 : Concurrent Access Anomalies Problems
Apply Rita’s Transaction Second? – 2B –
Multiple users must be able to update the system simultaneously.
Rita & Ken checking  $3, $3,050 $2,500
Suppose the Software at the teller windows starts to process Rita’s Transaction:
$ 3,000 - $500 = $2,500
Suppose at the same time, the Software at the drive through window starts to process Ken‘s Transaction:
$ 3,000 + $50 = $3,050
Also The Wrong Answer!

16. Problem # 5 : Concurrent Access Anomalies Problems
Correct Transaction Processing – 3A –
Multiple users must be able to update the system simultaneously.
Rita & Ken currently have $3,000 in their checking account.
Suppose the Software at the teller windows starts to process Rita’s Transaction: Lock The Record Containing CurrentCheckingBalance
Request - $500
Suppose at the same time, the Software at the drive through window starts to process Ken‘s Transaction:
Request $50

17. Problem # 5 : Concurrent Access Anomalies Problems
Correct Transaction Processing – 3B –
Multiple users must be able to update the system simultaneously.
Rita & Ken  CurrentCheckingBalance = $3, $3,050
Suppose the Software at the teller windows starts to process Rita’s Transaction: Lock The Record Containing CurrentCheckingBalance
Request - $500
Suppose at the same time, the Software at the drive through window starts to process Ken‘s Transaction:
Request $50
Both Requests Queued in Transaction Module  suppose Ken first!
Lock CurrentCheckingBalance Record
3,000 + $50 = $3,050
UnLock CurrentCheckingBalance Record

18. Problem # 5 : Concurrent Access Anomalies Problems
Correct Transaction Processing – 3C –
Multiple users must be able to update the system simultaneously.
Rita & Ken  CurrentCheckingBalance = $3, $3,050 $2,550
Suppose the Software at the teller windows starts to process Rita’s Transaction: Lock The Record Containing CurrentCheckingBalance
Request - $500
Suppose at the same time, the Software at the drive through window starts to process Ken‘s Transaction:
Request $50
Both Requests Queued in Transaction Module  suppose Rita’s second
Lock CurrentCheckingBalance Record
3,050 - $500 = $2,550
UnLock CurrentCheckingBalance Record
Right Answer!

19. Problem # 6 : Security Problems
Not every computer user should have access to all of the records.
All records should be accessible on an "as-needed basis"
Employee Payroll Tables
Loan Records Tables
Customer Account File
Cumulative Bank Tables
Etc.
???
Teller

20. Problem # 7 : Integrity Problems
Some individual data items must be always be within certain constraints.
The balance on the Savings Account must never be less than $0.00
The balance on the Checking Account with a $ overdraft limit must never be less than -$500.00
The number of children should never be less than 0
The age should never be less than 0 years
The month shall never be less than 1 or greater than 12
Etc.

21. Computer Science Department
Database Systems CSCI 3343
Dr. Thomas E. Hicks
Computer Science Department
Trinity University
Textbook: Database System Concepts
By Silberschatz, Korth, Sudarshan