1. Physical Database Design and Performance
Ali Saeed Khan
13/12/2017

2. Physical Database Design and Performance
Denormalization

3. Denormalization
The process of transforming normalized relations into non normalized physical record specifications.
One to one
Many to many
Reference Data (One to many)

4. 2 entities with 1-1 Relationship
If access frequency between these two entities is high
Note: Fields from the optional entity must have NULL values allowed

5. 2 entities with 1-1 Relationship

6. Many-to-Many Relationship
2 Joins, Reduce one most frequent join by combining the 2 entities

7. Many-to-Many Relationship

8. Reference Data (1-M)
Reference data exists in an entity on the one side of a one-to-many relationship, and this entity participates in no other database relationship.
WHEN, few instances of the entity on many side for each entity instance on the one side.

9. Reference Data

10. Physical Database Design and Performance
partitioning

11. Partitioning
This is a form of denormalization involves creation of more tables by partitioning a relation into multiple physical tables
Horizontal
Vertical

12. Horizontal Partitioning
Implements a logical relation as multiple physical tables by placing different rows into different tables, based on common column values.
E.g. Library Books, placed type wise.
Or, customer table on region
Common methods of horizontal partitioning
Single column value
date

13. Horizontal Partitioning
Advantages,
Efficiency
Local Optimization
Security
Recovery and Uptime
Load Balancing
Disadvantages
Inconsistent access speed
Complexity
Extra Space and Update time

14. Horizontal Partitioning
Same as (super-type/subtype)
WHEN, when the partitioned tables are used in different ways i.e. queries, transactions and reports.
Should not be if partitioned are used in same way

15. Horizontal Partitioning
Oracle
Range Partitioning
Hash (rows are distributed evenly)
List (partition column has a list of values)

16. Horizontal Partitioning

17. Vertical Partitioning
Distributes the columns of a logical relation into separate tables, repeating the PK in each of the tables
Usually Operation related columns are kept together e.g. accounting, sales, engineering.
Also depends upon access analysis………
Neither H nor V partitioning prohibits the ability to treat the original relation as a whole.

18. Vertical Partitioning

19. Data Replication
Same data is stored at multiple places in the same database…..
Must be used with great care and analysis
Only used when the data is very frequently used

20. Designing physical database files
Physical Database Design and Performance
Designing physical database files

21. Physical File
A named portion of secondary memory allocated for the purpose of storing physical records.
In order to optimize the performance of the database processing, the person who administers a database, often need to know the extensive details about how the DB management system manages physical storage space.
This knowledge is DBMS specific but the broad concepts can be applied to all.

22. Tablespace
A named logical storage unit in which data from one or more database tables, views, or other database objects may be stored.
Oracle e.g.
(SYSTEM and SYSAUX) for system data (data dictionary and meta data)
(TEMP) for temporary workspace
(UNDOTBS1) for undo operations
For user business data (more than one)

23. Tablespace
Helps admin maintain security, as each database in DBMS has a separate tablespace for which unique users can be created
Each tablespace is logically divided into,
Segments
Then extents
Data blocks (smallest unit of storage)
Each tablespace can have multiple data files, but each file belongs to a unique tablespace and DB

24. Physical Database Design and Performance
File organizations

25. File Organizations
A technique for physically arranging the records of a file on secondary storage devices.
We don’t need to design file organization however we have to make selection of an organization and its parameters for a table or a physical file.

26. Factors Fast Data Retrieval
High throughput for processing data input and maintenance transactions
Efficient use of storage space
Protection from failures or data loss
Minimizing need for reorganization
Accommodating growth
Security from unauthorized use

27. File Organization

28. Sequential File Organization
Because of their inflexibility sequential files are not used in DB but may be used for files that backup data from database

29. Sequential File Organization

30. Indexed File Organization
Records are saved either sequentially or non-sequentially, an indexed is maintained which allows application to access these records individually
INDEX: A table or other data structure used to determine in a file the location of records that satisfy some condition

31. Join Index
Indexes we studied till now are good for a limited set of records (few specific table rows)
Join index is used in data warehousing and other decision support application (DSA).
In DSA data accessing tends to want all rows that are related on a specific criteria
“An Index on columns from two or more tables that come from the same domain of values”

32. Join Index

33. Join Index

34. Join Index
A join index, similar to any other index, saves query processing time by finding data meeting a pre-specified qualification at the expense of the extra storage space and maintenance of the index.

35. Indexed File Organization

36. Hashed File Organization
A storage system in which address for each record is determined using a hashing algorithm (“A routine that converts a primary key value into a relative record number or relative file address”)

37. Hashed File Organization

38. Hashed File Organization
Hash clash (more than one key hashes to same address)
Hash Index Table (key is hashed into an index where pointer to actual data record is stored)

39. Comparison

40. Using and selecting indexes
Physical Database Design and Performance
Using and selecting indexes

41. Creating unique key index