System Design

1. System Analysis and Design System Design - Mr. Ahmad Al-Ghoul

2. learning Objectives • Explain data warehousing and data mining • Differentiate between logical and physical storage and records • Explain data control measures System Analysis and Design System Design

3. Data Storage and Access • Data storage and access involve strategic business tools, such as data warehousing and data mining software, as well as logical and physical storage issues, selection of data storage formats, and special considerations regarding storage of data fields System Analysis and Design System Design

4. Data Storage and Access • Strategic tools for data storage and access • Data warehousing • A data warehouse is an integrated collection of data that can support management analysis and decision making. • Data warehouses are used to organize information from many databases for quick and effective queries • Data warehouse can link various information systems and databases • In the data warehouse, data are organized around major subjects System Analysis and Design System Design

5. Data Storage and Access • Strategic tools for data storage and access • Data warehousing • Data in the warehouse are stored as summarized rather than detailed raw data • A data warehouse allows users to specify certain dimensions, or characteristics • By selecting values for each characteristics, a user can obtain multidimensional information from the stored data. For example, in a typical company, suppose that a user wants to see may 2005 sales results for specific sales rep like sally brown. The data is stored in two different systems: the sales information system and human resources information system • Without a data warehouse, it would be difficult for a user to extract data that spans several information systems and time frames System Analysis and Design System Design

6. Data Storage and Access A data warehouse stores data from several systems. By selecting data dimensions, a user can retrieve specific information without having to know how or where the data is stored. System Analysis and Design System Design

7. Data Storage and Access • Strategic tools for data storage and access • Data Mining • Data mining software looks for meaningful patterns and relationships among data. For example, data mining software could help a consumer products firm identify potential customers based on their prior purchases. • The enormous growth in e-commerce has focused attention on data mining as a tool to analyze Web visitor behavior and traffic trends • Data Mining Increase average pages viewed per session. System Analysis and Design System Design

8. Data Storage and Access • Strategic tools for data storage and access • Data mining is a valuable tool for managers who must make management decisions involving complex issues, because it can detect patterns and trends in large amount of data • In a recent article in New Architect, a Web-based magazine, Dan R. Greeing says that “ the great advantage of Web marketing is that you can measure visitors interactions more effectively than in brick-and-mortar stores or direct mail. Data mining works best when you have clear, measurable goals.” • Some of the goals he suggests are: • Increase number of referred customers • Reduce clicks to close, which means average number of page views to accomplish a purchase or obtain desired information. • Increase checkouts per visit • Increase average profit per checkout System Analysis and Design System Design

9. Data Storage and Access • Logical and Physical Storage • Logical storage • Refers to information as seen through a user's eyes, regardless of how or where that information is organized or stored. • A Character is A group of eight bits, or a byte. • A data element, field, or attribute is set of bytes, which is an individual fact about a person, place, thing, or event. • A data element, field, or attribute is the smallest piece of data that has meaning within an information system. • A logical record contains field values that describe a single person, place, thing, or event. • Application programs see a logical record as a set of fields, regardless of how or where the data is stored physically. System Analysis and Design System Design

10. Data Storage and Access • Logical and Physical Storage • Physical storage • Storage that is strictly hardware-related, because it involves the process of reading and writing binary data to physical media such as a hard drive or CD-ROM. • Physical storage involves • A physical record, or a block, is the smallest unit of data that is accessed by the operating system. • When the system reads a physical record, it loads the data from storage into a buffer • A buffer is a segment of computer memory used for temporary storage. • The actual number of logical records in a physical record is determined by the blocking factor • The blocking factor is the number of logical records in one physical record. System Analysis and Design System Design

11. Data Storage and Access A data file consists of physical records, or blocks, that contain logical records. You can see that each physical record consists of two logical records that means the blocking factor is 2 fields Logical records Physical records file System Analysis and Design System Design

12. Data Storage and Access • Data Storage Formats • Computers use four primary data storage format • EBCDIC • EBCDIC, which stands for Extended Binary Coded Decimal Interchange Code, a data storage method used on most mainframe computers. • ASCII • ASCII, which stands for American Standard Code for Information Interchange, A data storage method used on most minicomputers and personal computers. • Unicode • Unicode is a relatively recent coding method that represents characters as integers. Unlike EBCDIC and ASCII, which use eight bits for each character, Unicode requires 16 bits per character, which allows it to represent more than 65,000 unique characters. • Unicode is important for multinational versions of a program that will be sold in different countries with different languages System Analysis and Design System Design

13. Data Storage and Access • Data Storage Formats • Binary • Binary storage format: A format that offers efficient storage of numeric data. • Integer format • A type of binary storage format. The integer format requires two bytes to store numbers from –32,768 to 32,767. • Long integer format • A type of binary storage format. The long integer format can store numbers from –2,147,483,647 to 2,147,483,647 using only four bytes of storage. • Other binary formats exist for efficient storage of exceedingly long numbers System Analysis and Design System Design

14. Data Storage and Access • Selecting a Data Storage Format • In many cases, a user can select a specific data storage format • You can store documents, spreadsheets, and databases in Unicode-compatible form by using the font called Arial Unicode MS • When choosing numeric data formats, you should use a format that will be adequate for all possible current and future data • Each data storage format has advantages and disadvantages • Best answer is it depends on the situation System Analysis and Design System Design

15. Data Control • File and database control must include all measures necessary to ensure that data storage is correct, complete, and secure • A well-designed DBMS must provide built-in control and security features, including subschemas, passwords, encryption, audit trail files, and backup and recovery procedures to maintain data • Subschema can be used to provide a limited view of the database to a specific user, or level of users System Analysis and Design System Design

16. Data Control • DBMS control and security features • User ID and Password • A method of limiting access to files and databases to protect stored data by prove positively that the user is what he/she claims to be. • Permissions • User-specific privileges that determine the type of access a user has to a database, file, or directory. • Encryption • A process where data is coded (converted into unreadable characters) so that only those with the required authorization can access the data (usually via decoding software). System Analysis and Design System Design

17. Data Control • DBMS control and security features • Backup • The process of saving a series of file or data copies to be retained for a specified period of time. • Recovery procedures • Recovery procedures involve restoring data and restarting a system after an interruption. Recovery procedures can be used to restore a file or database to its current state at the time of the last backup. • Audit log files • Audit log files record details of all accesses and changes to a file or database and can be used to recover changes made since the last backup. • Audit fields • Audit fields are special fields within data records to provide additional control or security information. Typical audit fields include the date the record was created or modified, the name of the user who performed the action, and the number of times the record has been accessed. System Analysis and Design System Design

18. Sequence Summary • Data warehouse can link various information systems and databases • In the data warehouse, data are organized around major subjects • Data warehouse allow easy access via data mining software, that searches for patterns and identifies relationships not imagined human decision makers • Data mining software looks for meaningful patterns and relationships among data • Logical storage is information seen through a user’s eyes, regardless of how or where that information actually is organized or stored. • Physical storage is hardware-related and involves reading and writing blocks of binary data to physical media • A logical record is a related set of field values that describes a single person, place, thing, or event • A physical record consists of one or more logical records, depending on the blocking factor • Data storage formats include EBCDIC, ASCII, Unicode, and binary • File and database control measures include limiting access to the data, data encryption, backup/recovery procedures, audit-trail files, and internal audit fields System Analysis and Design System Design

19. Sequence Summary • In this Sequence we have • Explained Strategic tools for data storage and access including data warehousing and data mining • Differentiated between logical and physical storage and records • Explained the various types of data storage formats • Explained how to Select a Data Storage Format • Explained data control measures System Analysis and Design System Design

20. Reference [1] System Analysis and Design, Sixth Edition Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt Publisher: SHELLY CASHMAN SEWIES. System Analysis and Design System Design