FILE ORGANIZATION BIT Binary Digit 0 1 Y

FILE ORGANIZATION • BIT: Binary Digit (0, 1; Y, N; On, Off) • BYTE: Combination of BITS which represent a CHARACTER • FIELD: Grouping of characters int a word, group of words, or a complete number (column) • RECORD: Group of related fields (row) * 6. 1

FILE ORGANIZATION • FILE: A Collection of Similar RECORDS • DATABASE: A group of related files * 6. 2

Hierarchy User Dept Database User ID T 087 T 129 T 238 File User ID T 087 Record Field Byte Bit 6. 3 First Name Denise Last Name Basic Charge Dept Code Carr $10. 00 PLN User ID (T 087) 01001010 (Letter J in ASCII) 0

KEY FIELD: Field Used to Retrieve, Update, Sort RECORD KEY FIELD Field in Each Record Uniquely Identifies THIS Record For RETRIEVAL UPDATING SORTING * 6. 4

SEQUENTIAL VS. DIRECT FILE ORGANIZATION • SEQUENTIAL: Tape Oriented; One File Follows Another; Follows Physical Sequence • DIRECT: Disk Oriented; Can be Accessed Without Regard to Physical Sequence * 6. 5

FILING METHODS • INDEXED SEQUENTIAL ACCESS METHOD (ISAM) : – EACH RECORD IDENTIFIED BY KEY – GROUPED IN BLOCKS AND CYLINDERS – KEYS IN INDEX • VIRTUAL STORAGE ACCESS METHOD (VSAM) : – MEMORY DIVIDED INTO AREAS & INTERVALS – DYNAMIC FILE SPACE VSAM WIDELY USED FOR RELATIONAL DATABASES • DIRECT FILE ACCESS METHOD * 6. 6

DIRECT FILE ACCESS METHOD • EACH RECORD HAS KEY FIELD • KEY FIELD FED INTO TRANSFORM ALGORITHM • ALGORITHM GENERATES PHYSICAL STORAGE LOCATION OF RECORD (RECORD ADDRESS) * 6. 7

DATABASE MANAGEMENT SYSTEM (DBMS) SOFTWARE TO CREATE & MAINTAIN DATA ENABLES BUSINESS APPLICATIONS TO EXTRACT DATA INDEPENDENT OF SPECIFIC COMPUTER PROGRAMS * 6. 8 DBMS

COMPONENTS OF DBMS: • DATA DEFINITION LANGUAGE: – Defines data elements in database • DATA MANIPULATION LANGUAGE: – Manipulates data for applications • DATA DICTIONARY: – Formal definitions of all variables in database; controls variety of database contents 6. 9 * DBMS

6. 10

RELATIONAL DATA MODEL • • 6. 11 DATA IN TABLE FORMAT RELATION: TABLE TUPLE: ROW (RECORD) IN TABLE FIELD: COLUMN (ATTRIBUTE) IN TABLE *

SQL Definition: The standard data manipulation language for Relational database management systems. Example (code generated by our MS-Access project: SELECT [User Frank De. Wolf]. [User Id], [User Frank De. Wolf]. [First Name], [User Frank De. Wolf]. [Last Name], [User Frank De. Wolf]. [Phone Ext] FROM [User Frank De. Wolf] WHERE ((([User Frank De. Wolf]. [Basic Charge])=13)); 6. 12

TYPES OR RELATIONS ONE-TO-ONE: STUDENT CLASS ONE-TO-MANY: STUDENT A MANY-TO-MANY: 6. 13 ID STUDENT B CLASS 1 STUDENT A STUDENT C CLASS 2 STUDENT B STUDENT C

HIERARCHICAL DATA MODEL ROOT FIRST CHILD 2 nd CHILD 6. 14 Employer Compensation Ratings Salary Job Assignments Pension Benefits Insurance Health

NETWORK DATA MODEL • VARIATION OF HIERARCHICAL MODEL • USEFUL FOR MANY-TO-MANY RELATIONSHIPS * NETWORK 1 NETWORK A 6. 15 NETWORK 2 NETWORK B NETWORK C

DISTRIBUTED DATABASES • PARTITIONED: remote CPUs (connected to host) have files unique to that site, e. g. , records on local customers • DUPLICATE: each remote CPU has copies of common files, e. g. , layouts for standard reports and forms * 6. 16

DATABASE TRENDS • DATA WAREHOUSE: Organization’s electronic library stores consolidated current & historic data for management reporting & analysis • DATA MART: Small data warehouse for special function, e. G. , Focused marketing based on customer info * 6. 17

COMPONENTS OF DATA WAREHOUSE 6. 18

DATABASE ADMINISTRATION • DEFINES & ORGANIZES DATABASE STRUCTURE AND CONTENT • DEVELOPS SECURITY PROCEDURES • DEVELOPS DATABASE DOCUMENTATION • MAINTAINS DBMS * 6. 19