CSC 4402 Exam 1 Study Guide

CSC 4402 Exam 1 Study Guide - CSC 4402 10/12/2009 Page 1 of...

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CSC 4402 10/12/2009 Page 1 of 8 Midterm review Summary of contents covered before the midterm Chapters 1 – 4. Part 1 – Basic concepts – Chapter 1 Part 2 – The Relational Data model – Chapter 2 Part 3 – SQL – Chapters 3, 4 Part 1 – Basic concepts Chapter 1 – can skip sections 1.7, 1.9, 1.10 Homework 1 outlines the major concepts covered, but we’ll list them here anyway: Database systems o A set of data files o A set of programs for accessing the data files Main objectives o Environment for efficient and convenient access to data Data integration o Reduced redundancy o Ease of access Data integrity o Error free o Correctness of data Data sharing o Concurrent access to data DBMS – a collection of interrelated data and a set of programs to access those data. DBA – coordinates all the activities of the database system; the database administrator has a good understanding of the enterprise’s information resources and needs. DBA responsibilities include: o Schema definition o Storage structure and access method definition o Schema and physical organization modification o Granting user authority to access the database o Specify integrity constraints o Acting as liaison with users o Monitoring performance and responding to changes in requirements Advantages of DBMS vs. traditional file system approach o Reduced redundancy data is not stored in multiple locations and formats o Avoid data inconsistencies o Concurrency predictability in results of simultaneous reads/writes
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CSC 4402 10/12/2009 Page 2 of 8 o Avoids data isolation data is not stored in multiple locations and formats o Better data security o Better integrity constraint supports easier to define and change; not hard- coded into programs) o Convenient and efficient data access o Atomicity data is not left in an inconsistent state o Better support for data abstraction The ANSI/Sparc 3-level architecture. The main purpose of the 3-level architecture is to (i) provide data abstraction/independence and (ii) efficient access to data o View Application programs are at this level Closest to the user Individual user perspective Subschemas o Logical What data is in the db (schema) How the data in the db are related o Physical Where data is actually stored and retrieved from files Schema – logical structure of the database Instance – actual contents of the database at a given time Data independence (DI) o Physical DI Ability to change the physical schema without causing changes in the logical schema o Logical DI Ability to change the logical schema of the DB without causing changes in the view level sub-schemas so that existing application programs are not changed. This is much more difficult to accomplish than physical DI. The connection between the two levels of data independence and the 3-level
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This note was uploaded on 01/25/2010 for the course CSC 4402 taught by Professor Staff during the Spring '08 term at LSU.

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CSC 4402 Exam 1 Study Guide - CSC 4402 10/12/2009 Page 1 of...

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