Modern Database Management Study Guide

Exam 2 * The information needed for physical file and DB design include these requirements: 1) Normalized relations, including estimates for the range of the number of rows in each table 2) Definitions of each attribute, along with physical specifications such as maximum possible length 3) Descriptions of where and when data are used in various ways (entered, retrieved, deleted, and updated, including typical frequencies of these events) 4) Expectations or requirements for response time and data security, backup, recovery, retention, and integrity 5) Descriptions of the technology (DBMS) used for implementing the DB * Physical DB design requires several critical decisions that will affect integrity and performance of the application system: * Data Type: choosing the storage format for each attribute from the logical data model * Giving the DBMS guidance regarding how to group attributes from the logical data model into physical records * Giving the DBMS guidance regarding how to arrange similarly structured records in secondary memory (primarily hard disks), using a structure called a file organization, so that individual and groups of records can be stored, retrieved, and updated rapidly * Selecting structures, including indexes and the overall database architecture, for storing and connecting files to make retrieving related data more efficient * Preparing strategies for handling queries against the DB that will optimize performance and take advantage of the file organizations and indexes that you have specified * Field: is the smallest unit of application data recognized by system software, such as a programming language or database management system a field corresponds to a simple attribute in the logical data model * Data Type: is a detailed coding scheme recognized by system software, such as DBMS, for representing organizational data * Selecting data type involves 4 objectives: