1. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 1 Data Storage Design Chapter 11

2. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 2 Key Definitions The data storage function manages how data is stored and handled by programs that run the system Goals of data storage design Efficient data retrieval (good response time) Access to the information users need

3. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 3 DATA STORAGE FORMATS

4. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 4 Types of Data Storage Formats Files: electronic lists of data optimized to perform a particular transaction Database: a collection of groupings of information the relate to each other in some way. A Database Management System (DBMS) is software that creates and manipulates databases.

5. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 5 Appointment File

6. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 6 Appointment Database

7. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 7 File Attributes Files contain information formatted for a particular transaction Typically organized sequentially Pointers used to associate records with other records Linked Lists are files with records linked together using pointers

8. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 8 File Types Master files – store core, important information Look-up files – store static values Transaction files – store information that updates a master file Audit files – record before and after versions of data History (archive) files – store past information

9. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 9 Database Types Legacy database Hierarchical (depict parent-child relationships using inverted trees) Network (depict nonhierarchical associations using pointers) Relational database Object database Multidimensional database

10. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 10 Hierarchical Database Example

11. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 11 Network Database Example

12. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 12 Relational Database Concepts Popular; easy for developers to use Primary and foreign keys used to identify and link tables Referential integrity ensures correct and valid table synchronization Structured Query Language (SQL)- standard language for accessing data

13. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 13 Relational Database Example

14. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 14 Object Database Concepts Built around objects consisting of both data and processes Objects are encapsulated (self-contained) Object classes – major object categories OODBMS – used primarily for applications with multimedia or complex data Hybrid OODBMS – both object and relational features

15. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 15 Object Database Example

16. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 16 Multidimensional Database Concepts Stores data for easy aggregation and manipulation across many dimensions Used for data warehouses and data marts Summary data is pre-calculated and stored for fast access

17. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 17 Multidimensional Database Example

18. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 18 OPTIMIZING DATA STORAGE

19. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 19 Dimensions of Data Storage Optimization Conflicting goals: Storage efficiency (minimizing storage space) Speed of access (minimizing time to retrieve desired information)

20. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 20 Storage Efficiency Minimize null values and redundancy Reduce update anomalies Normalization process optimizes the data storage design for storage efficiency

21. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 21 Optimizing Data Storage Efficiency

22. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 22 Normalization Steps

23. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 23 Optimizing Access Speed Techniques available to increase access speed after optimizing for efficiency Denormalization Clustering Intrafile Interfile Indexing

24. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 24 Denormalization Add redundancy back to data storage design to reduce the number of joins performed in a query Ideal for frequently queried but rarely updated data Look-up tables 1:1 relationships Add parent attributes to child Star schema design data models

25. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 25 Clustering Reduce the number of times storage must be accessed by physically placing like records close together. Intrafile clustering – similar records in a table are stored together Interfile clustering – combine records from more that one table that are typically retrieved together

26. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 26 Indexing A minitable that contains values from one or more fields in a table and the location of the values within the table Similar to the index of a book.

27. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 27 Payment Type Index

28. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 28 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

29. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 29 Volumetrics – Estimating Data Storage Size Raw data – sum of the average widths of all fields in a table. Calculate overhead requirements based on DBMS vendor recommendations Estimate initial number of records Estimate growth rate of records

30. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 30 Estimating Data Storage Size FieldAverage Size (Characters) Order number 8 Date 7 Cust ID 4 Last name13 First name 9 State 2 Amount 4 Tax rate 2 Record Size49 Overhead (30%)14.7 Total Record Size63.7 Initial Table Size50,000 Initial Table Volume 3,185,000 Growth/Month 1,000 Table volume @ 3 years 5,478,200

31. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 31 Data Storage Size Estimator

32. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 32 Summary Files are electronic lists of data generally of five types: master, look-up, transaction, audit, and history. A database is a collection of groupings of information and a DBMS is software that creates and manipulates these. There are a number of methods for optimizing data access speed and data storage efficiency, though the designers may have to make tradeoffs between these goals.

33. PowerPoint Presentation for Dennis & Haley Wixom, Systems Analysis and Design, 2 nd Edition Copyright 2003 © John Wiley & Sons, Inc. All rights reserved. 11 - 33 Copyright © 2003 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for redistribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein.