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WHY DATABSES? 7 Traditional Programming Limitations That Encouraged Database Design Banking Application

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

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?

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:

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:

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:

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

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.

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?

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  $3,000 $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

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  $3,000 $2,500 $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!

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  $3,000 $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!

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  $3,000 $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!

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

Problem # 5 : Concurrent Access Anomalies Problems Correct Transaction Processing – 3B – Multiple users must be able to update the system simultaneously. Rita & Ken  CurrentCheckingBalance = $3,000 $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

Problem # 5 : Concurrent Access Anomalies Problems Correct Transaction Processing – 3C – Multiple users must be able to update the system simultaneously. Rita & Ken  CurrentCheckingBalance = $3,000 $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!

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

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 $500.00 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.

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