AIS Chapter 9: Database Management Systems

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)

relational tables

these can correct insertion, deletion, and update anomalies

data currency

Data will temporatily be inconsistent as records are read and updated. occurs in DDP with a centralized database during transaction processing.

database approach

________ __________ can be costly to implement and can only operate in certain environments

databse

________ processing resolves flat file problems of redundancy, storage, updating, currency of information, and task data dependency

insertion anomaly

a new item cannot be added to the table until at least one entity uses this item

update anomaly

anomaly in which modification on an attribute must be made in each of the rows in which an attribute appears

database processing

create a single data repository to support numerous applications

attributes

data elements that form columns

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

meta data

data that describes data

DBMS

databse management system

data dictionary

description of every data element in the database

flat file

disadvantage of this process is that creates redundant data and programs and varying formats for storing redundant data

does not

distributed data processing (DDP) does/does not mean decentralization because IPUs are connected to one another and coordinated

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

backup and recover

feature of DBMS that copies data in the event of an attack or system failure

database access

feature that allows authorized access to sections of the databse

direct query

feature that allows authorized users to access data without programming

database usage reporting

feature that captures statistics on database usage

application development

feature that has user created applications

user programs

feature that makes presence of DBMS transparent to users

Currency of Information

flat file potential problem of failing to update all the affected files

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

Task Data Dependency

flat file problem where user's inhability to obtain additional information as his/her needs change.

Structured Query Language

fourth generation langugue that has emerged as the standard query languate

deletion anomaly

happens if an attribute item that is used by only one entity is deleted. all informatin about that item is lost

distributed data processing

happens when data processing is distributed among several information processing units (IPUs) and distributed throughout the organization.

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

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

relational model

model that portrays data in the form of two dimensional tables

Data Base Planning

need internal and external information for this kind of planning

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

concurrency

presence of complete and accurate information at all iPU sites

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

database lockout

procedure necessary to keep out IPUs from reading incosistent dat and keep from writting over a transaction being written by another IPU

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

DBMS

purpose of this is to provide controlled access to the database

tuples

records that form rows

DBMS

special software system programmed to know which data elements each user is authorized to accesss and deny unauthorized requests.

flat file processing

specific data file created for each application

partitioning

splits distributed databases into segments that are distributed to their primary users.

relation

the database table

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

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

query capability

this permits end users and professional programmers to accss data in the database without the need for conventional programs

time stamping

used to sterilize all transactions so can see what happend first, in what order, and what needs to be updated.

hierarchical, network, relational, object oriented

what are the four types of logical data structures

flat file and database processing

what are the methods for designing interface between program instruction and data

insertion, deletion, and update

what are the three types of anomalies

must be linked by foreign keys

when un-normalized tables are split and reduced to third form, what must happen?