AIS Chapter 9: Database Management Systems

Data Base Planning
need internal and external information for this kind of planning
data dictionary
description of every data element in the database
meta data
data that describes data
flat file and database processing
what are the methods for designing interface between program instruction and data
flat file processing
specific data file created for each application
database processing
create a single data repository to support numerous applications
flat file
disadvantage of this process is that creates redundant data and programs and varying formats for storing redundant data
Data Storage
flat file problem that creates excessive storage costs of paper documents and or magnetic documents
Data Updating
flat file problem where any changes or additions must be performed multiple times
Currency of Information
flat file potential problem of failing to update all the affected files
Task Data Dependency
flat file problem where user’s inhability to obtain additional information as his/her needs change.
databse
________ processing resolves flat file problems of redundancy, storage, updating, currency of information, and task data dependency
database approach
________ __________ can be costly to implement and can only operate in certain environments
DBMS
databse management system
DBMS
special software system programmed to know which data elements each user is authorized to accesss and deny unauthorized requests.
user programs, direct query, application development, backup and recover, databse usage reporting, and database access.
Features of Database Management System…(UP,DQ,AD,B&R,DUR,DA)
user programs
feature that makes presence of DBMS transparent to users
direct query
feature that allows authorized users to access data without programming
application development
feature that has user created applications
backup and recover
feature of DBMS that copies data in the event of an attack or system failure
database usage reporting
feature that captures statistics on database usage
database access
feature that allows authorized access to sections of the databse
DBMS
purpose of this is to provide controlled access to the database
query capability
this permits end users and professional programmers to accss data in the database without the need for conventional programs
Structured Query Language
fourth generation langugue that has emerged as the standard query languate
logical data structures
method used to organize records in a database. objective is to develop a structure effeciently so that data can be accessed quickly and easily. four types of structures
hierarchical, network, relational, object oriented
what are the four types of logical data structures
relational model
model that portrays data in the form of two dimensional tables
relation
the database table
attributes
data elements that form columns
tuples
records that form rows
data
the intersectin of rows and columns
properly designed relational tables
these have no repeating values, all occurences of a row and column are a single value, attribute values in any column must be of the same class, each column in a given table must be uniquely named, each row in the table must be unique in at least one attribute
relational model data linkages with more than one table
in these, data are viewed as a collection of independent tables. Relations are formed by an attribute that is common to both tables in the relation
insertion, deletion, and update
what are the three types of anomalies
insertion anomaly
a new item cannot be added to the table until at least one entity uses this item
deletion anomaly
happens if an attribute item that is used by only one entity is deleted. all informatin about that item is lost
update anomaly
anomaly in which modification on an attribute must be made in each of the rows in which an attribute appears
relational tables
these can correct insertion, deletion, and update anomalies
advantages of relational tables
the following are all ___________ of __________ ___________: removes all anomalies, various items of interest are stored in separate tables, space used efficiently, and are very flexible
normalization process
process which systematically splits annormalized complex tables into smaller tables that meet two conditions: 1. secondary attributes dependent on primary attributes and 2. secondary attributes are independet of each other
must be linked by foreign keys
when un-normalized tables are split and reduced to third form, what must happen?
distributed data processing
happens when data processing is distributed among several information processing units (IPUs) and distributed throughout the organization.
does not
distributed data processing (DDP) does/does not mean decentralization because IPUs are connected to one another and coordinated
centralized database
data retained in a central location where remote IPUs send requests for data. central location services the needs of the remote IPUs and actual processing performed at IPUs
data currency
Data will temporatily be inconsistent as records are read and updated. occurs in DDP with a centralized database during transaction processing.
database lockout
procedure necessary to keep out IPUs from reading incosistent dat and keep from writting over a transaction being written by another IPU
partitioning
splits distributed databases into segments that are distributed to their primary users.
deadlock phenomenon
problem with partitioned databases. occurs when multiple sites lock each other out of data they are currently using. one site needs data and is locked out by another site. Need a special software to analyze and resolve the issue and transactions may be terminated and restarted
replication
duplication of an entire databse for multiple IPUs. effective for situations with a high degree of data sharing but no primary users. supports read only queries. traffic between sites is reduced. Downside: maintaining current information at all locations is difficult
concurrency
presence of complete and accurate information at all iPU sites
time stamping
used to sterilize all transactions so can see what happend first, in what order, and what needs to be updated.
database administrator
person responsible for managing database resource. With multiple users sharing a common database requires organization coordination, rules, and guidelines to protect the integrity