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Object Persistence Design. Chapter 13. Key Definitions. Object persistence involves the selection of a storage format and optimization for performance. Four basic formats used for object persistence are: files, OO databases, object-relational, and relational databases.

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Presentation Transcript
key definitions
Key Definitions
  • Object persistence involves the selection of a storage format and optimization for performance.
  • Four basic formats used for object persistence are: files, OO databases, object-relational, and relational databases.
files
Files
  • Sequential Access
    • Data stored in order based on a particular attribute
    • Typically efficient for reports using all or most of the file’s data
  • Random Access
    • Data stored in unordered fashion
    • Typically efficient for finding individual records
other files
Other files
  • Master files
  • Transaction files
  • Audit
  • History
  • Look-up
customer order file
Customer Order File

Figure 13-1 Goes Here

relational databases
Primary key

Foreign key

Referential integrity

Structured Query Language (SQL)

Tables

Joining tables

Objects must be converted so they can be stored in a table

Relational Databases
object relational databases
Relational databases extended to handle the storage of objects

Use of user-defined data types

Extended SQL

Inheritance tends to be language dependent

Object-Relational Databases
relational database example
Relational Database Example

Figure 13-3 Goes Here

object oriented databases
Two approaches

Adding persistence extensions to OO languages

Separate database management systems

Extents

Object ID assigned

Some inheritance

Repeating groups or multivalued attributes

Mainly support multimedia applications

Sharp learning curve

Object-Oriented Databases
initial points to consider
Initial Points to Consider
  • Adding primary and foreign keys
    • Unless they add too much overhead
  • Data management functionality only in classes at datamanagement layer
    • May add overhead, but aids in portability and reuse
maintain a clean problem domain layer
Modifying the problem domain layer can create problems between the system architecture and human computer interface layer

The development and production costs of OODBMS may offset the production cost of having the data management layer implemented in ORDBMS

Maintain a Clean Problem Domain Layer
dimensions of data storage optimization
Dimensions of Data Storage Optimization
  • Storage efficiency (minimizing storage space)
  • Speed of access (minimizing time to retrieve desired information)
optimizing storage efficiency
Optimizing Storage Efficiency
  • Reduce redundant data
  • Limit null values
    • Multiple possible interpretations can lead to mistakes
  • A well-formed logical data model does not contain redundancy or many null values
optimizing access speed
Denormalization

Clustering

Intra-file

Inter-file

Indexing

Optimizing Access Speed
guidelines for creating indexes
Guidelines for Creating Indexes
  • Use indexes sparingly for transaction systems
  • Use many indexes to increase response times in decision support systems
  • For each table
    • Create a unique index based on the primary key
    • Create an index based on the foreign key
  • Create an index for fields used frequently for grouping, sorting, or criteria
estimating data storage size
Estimating Data Storage Size

Field Average Size (Characters)

Order number 8

Date 7

Cust ID 4

Last name 13

First name 9

State 2

Amount 4

Tax rate 2

Record Size 49

Overhead (30%) 14.7

Total Record Size 63.7

Initial Table Size 50,000

Initial Table Volume 3,185,000

Growth/Month 1,000

Table volume @

3 years 5,478,200

summary
Summary
  • There are four basic types of object persistence formats: files (sequential and random access), object-oriented databases, object-relational databases, and relational databases.
  • Tradeoffs between the formats make it necessary to consider which to apply in each environment
  • Once the format has been selected, data storage needs to be optimized for efficiency and speed of access.