1. A E-R Model for Online Flower Store
Product
Code
Occasion
code
Description
description
Name
Unit price
Occasion
address
Picture
Products N 1
Receivers M M 1
Orders
Customer ID 1
Order Date M M
address
Order Number
Order lines
Buyers M 1
Credit card
Product
Code
Customer ID
Name
Order
Number
quantity

2. A Simplified E-R Model Product Code Description Occasion code
Unit price
Occasion
Picture
Receiver Name
Products N M
Receiver address 1
Order Number
Credit card # M
Order lines M 1
Order Date
Orders
address M
Customer
Product
Code 1
Password
Order
Number
Customer
Name
quantity
Phone Number

3. Simplified Tables PRODUCTS USAGE CUSTOMER Customer_Name(Primary Key)
Product_Code (Primary Key)
Product_Name
Unit_Price
USAGE
Product_Code (Concatenated Key)
Occasion (Concatenated Key)
CUSTOMER
Customer_Name(Primary Key)
Password
Address
Phone_Number

4. Tables ORDERS ORDERLINE Order_Number (Primary Key) Order_Date
Customer Name (Foreign Key)
Receiver Name
Receiver Address
Credit_Card_Type
Credit_Card_Num
Credit_Card_Expiry
ORDERLINE
Order_Number (Concatenated Key)
Product_Code (Concatenated Key)
Quantity

5. Functional Dependence
PRODUCT (3NF)
Product_Code  Product Name,Unit Price
USAGE (BCNF)
CUSTOMER (3NF)
CustomerID  Name, Address, password, phone number
ORDERS (2NF)
Order Number  CustomerID, Order Date, Receiver Name,…
CreditCardNum  CreditCardExpiry (transitive dependence)
Receiver Name  Receiver Address (transitive dependence)
ORDERLINE (3NF)
ProductNumber + OrderNumber  Quantity

6. Transaction Processing

7. Transaction
A transaction is a sequence of steps that constitute some well-defined business activities
Transaction boundaries - the logical beginning and end of transactions
Commit changes for successful transactions
Reject changes for aborted transactions

8. Embedded SQL SQL can be embedded in host languages : PL/I, COBOL, etc.
SQL statements are prefixed by EXEC SQL
Use EXEC SQL DECLARE to define tables, views, and cursors
In SQL, use prefix “:” to reference host variables
Return feedback information through SQLCA

9. SQLCA
SQLCA SQL Communication Area SQLCODE 0 success, +100 no data found, <0 error EXEC SQL INCLUDE SQLCA IF SQLCODE < 0 THEN ....
Reference: C.J. Date, A Guide to DB2 , ch

10. Example of Embedded SQL
DCL GIVENS# CHAR(5) ; DCL RANK FIXED BIN(15) ; DCL CITY CHAR(15) ; EXEC SQL DECLARE S TABLE (S# CHAR(5) NOT NULL, SNAME CHAR(20), STATUS SMALLINT, CITY CHAR(15) ; EXEC SQL INCLUDE SQLCA ; GET LIST (GIVENS# ) ; EXEC SQL SELECT STATUS, CITY INTO :RANK, :CITY FROM S WHERE S# = :GIVENS# ; IF SQLCODE = 0 THEN PUT SKIP LIST (RANK, CITY);

11. Example of Embedded SQL
Update: EXEC SQL UPDATE S SET STATUS = STATUS + :RAISE, WHERE CITY = ‘LONDON’ ;
Delete: EXEC SQL DELETE FROM S WHERE STATUS = NULL ;
Insert: EXEC SQL INSERT INTO S (S#, SNAM E, STATUS, CITY) VALUES(:NEWS#, :NEWSNAME, :NEWSTATUS,'LONDON’) ;

12. Using Cursors for Sequential Access
Declare a cursor and use it as a sequential file of the query results EXEC SQL DECLARE X CURSOR FOR SELECT S#, SNAME, STATUS FROM S WHERE CITY = :PCITY FOR UPDATE OF STATUS ; GET LIST (PCITY, GIVENINC); EXEC SQL OPEN X ; DO WHILE ( SQLCODE = 0 ) EXEC SQL FETCH X INTO :PS#, :PSNAME, :PSTATUS; PUT SKIP LIST(PSNAME, PS#, PSTATUS); EXEC SQL UPDATE S SET STATUS = STATUS + :GIVENINC WHERE CURRENT OF X END; EXEC SQL CLOSE X ;

13. Integrity Control in SQL
Change supplier # of supplier SX from SX to SY in both tables S and SP. TRANEX: PROC OPTIONS (MAIN) : EXEC SQL WHENEVER SQLERROR GO TO UNDO; GET LIST(SX, SY); EXEC SQL UPDATE S SET S# = :SY WHERE S# = :SX; EXEC SQL UPDATE SP SET S# = :SY WHERE S# = :SX; EXEC SQL COMMIT; GO TO FINISH; UNDO: EXEC SQL ROLLBACK; FINISH: RETURN; END TRANEX;

14. Desired Transaction Properties
Atomicity -- All operations of a transaction must be completed. If not, the transaction is aborted.
Durability -- When a transaction is completed, the database reaches a consistent state which cannot be lost.
Serializability -- The concurrent transaction are treated as though they were executed in serial order.
Isolation -- The data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.

15. Concurrent Transactions
When transactions are interleaved, errors will occur in updating unless the DBMS has features to prevent interference between transactions
CUST A
BAL
100 1 2
GET CUSTA
GET CUSTA A
100 A
100
BAL : BAL - 50
BAL : BAL + 25 A 50 A
125
STORE CUSTA
STORE CUSTA 3 A 50 4 A
125

16. Problems with Concurrent Transactions
Lost updates - T2 is executed before T1 is committed
Uncommitted data -- T1 is rolled back after T2 accessed the uncommitted data
Inconsistent retrievals - - T1 calculates some summary data while T2 is updating the data

17. Concurrency Control - the Scheduler
Establish the order in which the operations in concurrent transactions are executed without causing inconsistency
Locking Guarantee exclusive use of a data item to a current transaction
Timestamping Assign a global unique timestamp to each transaction. Execute operations in timestamp order.

18. Resource Locking Lock granularity Lock Types Two-Phase Locking
Database level, Table level, Page level, Row level, Field level
Lock Types
Binary locks -- locked ,Unlocked
Shared/Exclusive Locks -- Unlocked, Shared (Read) lock, Exclusive (Write) lock
Two-Phase Locking
A growing phase
A shrinking phase

19. Deadlock Deadly embrace
Deadlock prevention:lock all required records at beginning of transaction
Deadlock resolution:back out of one of transactions and start again
User A
Lock X
Wait for Y
User B
Lock Y
Wait for X X Y

20. Optimistic vs. Pessimistic Locking
Optimistic locking
Assume the majority of database operations do not conflict.
Process each transaction in three phases: read, validation, and write.
Less restriction, may repeat process
Pessimistic locking
Assume the conflicts most likely will happen.
Lock, process, and unlock.
More restriction, no repeat process

23. Database Recovery
Database may be damaged or lost because of some system failure. The DBMS must provide mechanisms for restoring a database quickly and accurately after loss or damage.
System failures: machine failures disk head crashes program bugs incorrect operation

24. Database Recovery DBMS Database change log Database (current)
Transaction
log
before image
Database
(backup)
after image

26. Basic Recovery Facilities
Backup facilities Provide periodic backup copies of the entire database
Journalizing facilities Maintain an audit trail of transactions and database changes
Checkpoint facility Periodically suspends all processing and synchronizes its files and journals
Recovery manager Allows the DBMS to restore the database to a correct condition and restart processing transactions

27. Recovery via Restore/Rerun
Restore the latest backup copy
Reprocess the day’s transactions (up to the point of failure) against the backup copy of the database
Simple procedure
Time to reprocess transactions may be prohibitive
Sequencing of reprocessed transactions may be different from the original

28. Recovery via Roll Back/Roll Forward
New
Old
Roll Back
(Removing Database Changes)
Database
with
changes
Database
without
changes
Undo
Before
images
Old
(saved)
Roll Forward
(Repeating Database Changes)
New
Database
without
changes
Database
with
changes
Redo
After
images

30. Recovery Strategies
Aborted transactions (i.e. communication interruption) Backward recovery
Incorrect data Backward recovery or add compensation transactions
System failure (database is not damaged) Restart from the most recent checkpoint before the system failure, roll forward.
Database destruction (database damaged) Restore backup copy. Forward recovery to the check point before the loss occurred. Reprocess transactions after the check point.

31. Security Control
Security refers to the protection of data against unauthorized disclosure, alteration, or destruction
Physical security
Password security
Authentication schemas: biometric devices, smart card

32. Security Control Views or subschemas User-defined procedures
Authorization rules
Audit trails
Data encryption

34. Authorization Rules
Grant select on Staff to User01 Revoke update on Staff from User02
Authorization rules
Subject
Sales
department
Order
transactions
Object
Customer
record
Action
Insert
Read
Constraint
Credit limit
<= 5000
None

36. Database Administration
A critical success factor in managing the data resource in an organization
An indication of top management’s commitment to data resource management

37. DA and DBA
Data Administrator (DA) Responsible for controlling the overall corporate data resource, both computerized and non-computerized. Strong managerial orientation with company-wide scope.
Database Administrator (DBA) Responsible for the control of the centralized and shared database. Tends to be more technically oriented and has a narrower, DBMS-specific scope.

38. DBA Placement
Should not be organizationally below any group on which it imposes restrictions.
Should not be more than one level above the organizations with which it interfaces.

39. Desired DBA Skills Managerial Technical Broad business understanding
Coordination skills
Analytical skills
Conflict resolution skills
Communication skills
Negotiation skills
Broad data processing background
Systems Development Life Cycle
Structured methodologies
Database Life Cycle
Database design and modeling skills
Data dictionary management

40. DBA’s Managerial Role
Support the end-user community, resolve conflicts
Enforce policies, procedures, and standards for data creation, usage, distribution, and deletion within the database.
Control data security, privacy, and integrity Data are protected, reconstructable, auditable, tamperproof. Users are identifiable, authorized, monitored.
Plan, test, and Implement data backup and recovery Database security officer (DSO), Disaster management
Ensure data be distributed to the right persons at the right time in the right format.

41. DBA’s Technical Role
DBMS and utilities selection, evaluation ,and installation
Design and implementation of databases and applications
Testing and evaluation of databases and applications
Operation of the DBMS, utilities, and applications System support, performance monitoring and tuning, backup and recovery, security auditing and monitoring
Training and supporting users to use DBMS
Maintenance of the DBMS, utilities, and applications Storage reorganization, software upgrade, data migration and conversion

42. Database Administration Tools
Data Dictionary Stores the definition of data characteristics and relationships. May be integrated or stand-alone, active or passive. A tool for information resource management. The basis for monitoring database use and the assignment of access rights to the database users. Support data analysis-and-design activities
CASE Tools

43. Database Administration Tools
The Data Dictionary
Different types of data dictionaries:
An integrated data dictionary is included with the DBMS, while a stand-alone data dictionary comes from a third-party vendor.
An active data dictionary is automatically updated by the DBMS, while a passive data dictionary requires a batch process to create and update the dictionary. 40

44. Database Administration Tools
CASE Tools
CASE -- Computer-Aided Software Engineering
It provides an automated framework for the Systems Development Life Cycle.
Front-end CASE tools provide support for the planning, analysis, and design phases.
Back-end CASE tools provide support for the coding and implementation phases.
It is based on the use of structured methodologies and powerful graphical interfaces. 45

45. Database Administration Tools
CASE Tools
Benefits of CASE tools
A reduction in development time and costs
The automation of the SDLC
Standardization of the systems development methodologies
Easier maintenance of application systems developed with CASE tools
Improve communications among the DBA, applications designers, and the end users. 46

46. Database Administration Tools
CASE Tools
A CASE tool keeps track of all objects created by the systems designer in the data dictionary.
Some CASE tools provide interfaces that interact with the DBMS.
The CASE tool integrates all systems development information in a common repository. 47

47. Database Administration Tools
Commercial CASE Tools
Excelerator from Intersolv, Inc. provides five components:
Graphics designed to produce structured diagrams as data flow diagrams and E-R diagrams.
Screen painters and report generators to produce the information system’s input/output formats.
An integrated repository for storing and cross-referencing the system design data.
An analysis segment to provide a fully automated check on system consistency, syntax, and completeness.
A program document generator. 48

48. Database Administration Tools
Commercial CASE Tools
ERwin by LogicWorks
It produces fully documented E-R diagrams that can be displayed at different abstraction levels.
It is able to produce detailed relational designs.
Major relational DBMS vendors, such as ORACLE, provide fully integrated CASE tools for their own DBMS software as well as for RDBMSs supplied by other vendors. 50

49. Future Trend
The development of distributed databases may force an organization to decentralize the data-administration function further.
The introduction of an object-oriented DBMS is very likely to add more coding in the DBA’s data modeling and design activities, thus expanding and diversifying the DBA’s job.
The rapid spread of microcomputers and local area networks tends to diffuse operational control over data, thus making centralized data administration more difficult.