02 Database Systems PART2 — Transcript

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1. 0:01this is the continuation of the topic
2. 0:03database systems
3. 0:05databases evolve from the need to manage
4. 0:08large amounts of data
5. 0:10in an organized and efficient manner in
6. 0:12this discussion you will also learn how
7. 0:14the database system approach
8. 0:17helps eliminate most of the shortcomings
9. 0:20of file system data management
10. 0:26critique of the file system method
11. 0:28serves two major purposes
12. 0:30one understanding the shortcomings of
13. 0:32the file system
14. 0:33enables you to understand the
15. 0:35development of modern databases
16. 0:38two failure to understand such problems
17. 0:41is likely to lead to their duplication
18. 0:43in a database environment
19. 0:45even though database technology makes it
20. 0:47easy to avoid them
21. 0:49the following problems associated with
22. 0:51file systems
23. 0:53severely challenged types of information
24. 0:56that can be created from the data
25. 0:58as well as the accuracy of the
26. 0:59information
27. 1:01lengthy development times difficulty of
28. 1:04getting quick answers
29. 1:06complex system administration lack of
30. 1:09security
31. 1:10and limited data sharing extensive
32. 1:12programming
33. 1:19a file system exhibits structural
34. 1:21dependence
35. 1:22which means that access to a file is
36. 1:25dependent on its structure
37. 1:27for example adding a customer date of
38. 1:29birth field
39. 1:30to the customer file would require all
40. 1:33of the file system programs
41. 1:35must be modified to conform to the new
42. 1:37file structure
43. 1:39while structural independence
44. 1:42exists when you can change the file
45. 1:44structure without
46. 1:46affecting the application's ability to
47. 1:48access the data
48. 1:54data dependencies and data access
49. 1:56changes when data storage
50. 1:58characteristics change
51. 2:00data independence is a data storage
52. 2:04characteristics or change
53. 2:05without affecting the program's ability
54. 2:08to access the data
55. 2:10the practical significance of data
56. 2:12dependence
57. 2:13is the difference between the logical
58. 2:15data format
59. 2:16or how the human being views the data
60. 2:20in the physical data format or how the
61. 2:23computer
62. 2:24must work with the data
63. 2:30the pulse system structure makes it
64. 2:32difficult to combine data
65. 2:34from multiple sources and its lack of
66. 2:36security renders the file system
67. 2:38vulnerable to security bridges the
68. 2:41organizational structure promotes the
69. 2:43storage of the same basic data
70. 2:45in different locations database
71. 2:48professionals use the term
72. 2:51islands of information for such
73. 2:53scattered data locations
74. 2:55in a file system the entire sales
75. 2:58department would share access to the
76. 3:00sales data file
77. 3:01through the data management and
78. 3:03reporting programs created
79. 3:05by the data processing specialist
80. 3:08because data stored in different
81. 3:10locations
82. 3:11will probably not be updated
83. 3:13consistently
84. 3:15the islands of information often contain
85. 3:18different versions of the same data
86. 3:22data redundancy increases the
87. 3:24probability of having different versions
88. 3:26of the same data
89. 3:31the possible results of uncontrolled
90. 3:33data redundancy
91. 3:34are poor data security data
92. 3:38inconsistency
93. 3:40data entry errors and data integrity
94. 3:44problems
95. 3:46the dictionary defines anomaly as an
96. 3:48abnormality
97. 3:50ideally a field value change should be
98. 3:53made
99. 3:54in only a single place data redundancy
100. 3:57however
101. 3:58fosters an abnormal condition by forcing
102. 4:01field value changes
103. 4:02in many different locations a data
104. 4:05normally develops
105. 4:07when not all of the required changes in
106. 4:10the redundant data are made successfully
107. 4:13data anomalies are commonly defined as
108. 4:15values
109. 4:16update anomalies insertion anomalies
110. 4:19deletion anomalies
111. 4:25the problems inherent in file systems
112. 4:28make using a database systems very
113. 4:31desirable
114. 4:32unlike the file system with its many
115. 4:34separate and unrelated files
116. 4:37the database system consists of
117. 4:39logically related data stored
118. 4:41in a single logical data repository the
119. 4:44logical
120. 4:45label reflects the fact that the data
121. 4:48repository appears to be
122. 4:50a single unit to the end user even
123. 4:53though data might be physically
124. 4:55distributed among multiple storage
125. 4:57facilities
126. 4:58and locations dbms eliminates most of
127. 5:01the file systems data inconsistency
128. 5:04data anomaly data dependence and
129. 5:07structural dependence problems
130. 5:10current generation dbms software stores
131. 5:13data structures
132. 5:14relationships between structures and
133. 5:17access paths
134. 5:18also it defines stores and manages all
135. 5:21access paths in components
136. 5:27in figure 1.10 the databases dbms
137. 5:31provides numerous advantages
138. 5:33over file system management by making it
139. 5:36possible to eliminate most of the file
140. 5:38systems
141. 5:39data inconsistency data anomaly
142. 5:42data dependence and structural
143. 5:44dependence problems
144. 5:46the current generation of dbms software
145. 5:49stores not only the data structures but
146. 5:52also the relationships between those
147. 5:54structures and the access paths to those
148. 5:56structures
149. 5:57all in a central location the current
150. 6:00generation of dbms software also takes
151. 6:03care of
152. 6:03defining storing and managing all
153. 6:06required access paths to those
154. 6:08components
155. 6:13the term database system refers to an
156. 6:15organization of components that define
157. 6:18and regulate the collection storage
158. 6:20management and use of data within a
159. 6:23database environment
160. 6:24from a general management point of view
161. 6:27the database system is composed of the
162. 6:29five major parts
163. 6:30hardware software people procedures and
164. 6:34data
165. 6:38figure 1.11 illustrates the five
166. 6:40components of database system
167. 6:42environment
168. 6:44hardware refers to all the systems
169. 6:46physical devices
170. 6:47software is a dbms itself three types of
171. 6:50software
172. 6:51are needed to make the database system
173. 6:53fully functional
174. 6:55operating system dbms and application
175. 6:58programs and utilities
176. 7:00people includes all users of the
177. 7:02database system
178. 7:04primarily the five types of users can be
179. 7:06identified
180. 7:08are system administrators database
181. 7:11administrators
182. 7:12database designers system analysts
183. 7:16and programmers and end users
184. 7:19procedures are the instructions and
185. 7:21rules that govern the design
186. 7:23and use of the database system the word
187. 7:26data
188. 7:27covers the collection of effects stored
189. 7:30in the database
190. 7:38a dbms performs several important
191. 7:40functions that guarantee the integrity
192. 7:43and consistency
193. 7:44of a data in the database most of those
194. 7:46functions are transparent to end users
195. 7:49and most can be achieved only through
196. 7:51the use of a dbms
197. 7:52this includes data dictionary management
198. 7:56the dbms stores definitions of the data
199. 7:59elements in their relationships
200. 8:01or metadata in a data dictionary
201. 8:04data storage management the dbms creates
202. 8:08and manages the complex structures
203. 8:10required for data storage performance
204. 8:13tuning relates to the activities
205. 8:16that make the database perform more
206. 8:20efficiently in terms of storage and
207. 8:22access speed
208. 8:23data transformation and presentation
209. 8:26the dbms transforms entered data to
210. 8:29conform to the required data structures
211. 8:33security management the dbms creates a
212. 8:36security system that enforces
213. 8:39user security and data privacy
214. 8:45to continue with important functions of
215. 8:47dvms which includes
216. 8:49multi-user access control is for
217. 8:52sophisticated algorithms ensure
218. 8:54that multiple users can access the
219. 8:56database concurrently
220. 8:58without compromising its integrity
221. 9:01backup and recovery management
222. 9:03which enables recovery of the database
223. 9:06after a failure
224. 9:08data integrity management minimizes
225. 9:10redundancy and maximizes consistency
226. 9:17other included database functions are
227. 9:20database access languages
228. 9:22and application programming interfaces
229. 9:24the dvms provides
230. 9:26data access through a query language a
231. 9:29query language
232. 9:30is a non-procedural language one that
233. 9:33lets the user specify
234. 9:35what must be done without having to
235. 9:37specify how
236. 9:38structured query language or sql is the
237. 9:41de facto query language
238. 9:43and the data access standard supported
239. 9:46by the majority of dbms vendors
240. 9:49another is the database communication
241. 9:51interface
242. 9:52which is the current generation dbms
243. 9:55that accepts
244. 9:56end-user requests via multiple
245. 9:59different network environments
246. 10:04although the database system yields
247. 10:06considerable
248. 10:07advantages over previous data management
249. 10:10approaches
250. 10:11database systems do carry significant
251. 10:13disadvantages
252. 10:15like increased costs management
253. 10:18complexity
254. 10:19maintaining currency vendor dependence
255. 10:23frequent upgrade or replacement cycles
256. 10:29there we have it the fundamentals of
257. 10:31database
258. 10:33our next topic is about data models
259. 10:35where you will learn different
260. 10:37approaches to data management and how
261. 10:39these approaches
262. 10:40influence redesigns