Database: Architecture

ØFile Servers ØDatabase Servers ØCompute Servers ØCommunication Servers ØInternet Servers ØMail Servers ØObject Servers ØPrint Servers ØApplication Servers ØVideo Servers

What are the categories of servers?

concurrency no global clock independence failure server forms bottleneck server forms single point of failure database scaling is difficult security

What are the disadvantages of client/server architecture?

external, logical, and internal

What are the levels of the three-schema architecture?

SQL API database driver protocol stack server software remote database administration

What are the relational middleware categories?

classical, transactional-oriented RPC message-oriented specialized

What are types of middleware?

to separate user applications and physical database

What is the main goal of the three-schema architecture?

logical data independence

What property shields users from changes in the logical structure of the data or changes in the choice of relations to be stored?

F

What type of operations performed better at the server level... a)Manipulations of data b)Evaluation of query c)Concurrency d)Recovery e)Only a, b, c f)All of the above

The application programs need not to be changed since they refer to the external schema

When a schema at a lower level is changed, only the mappings between this schema and higher-level schemas need to be changed in a DBMS that fully supports data independence. What does this mean?

D

Which of the following main characteristics of database approach is not presented by Three-Schema Architecture. A) Self-describing nature of a database system B) insulation between programs and data, and data abstraction C) Support of multiple views of the data D) Sharing of data and multi-user transaction processing

schema diagram

a diagrammatic display of a database schema

data model

a set of concepts to describe the structure of a database, and certain constraints that the database should obey

index

aka an access path is a structure that makes the search for a particular database records efficient

data independence

allows application insulation that is the ability to change the schema at one level of a database without having to change the schema at the next level.

mappings

among schema levels are needed to transform requests and data it allows data independence by referring programs at the external level to the internal one for execution

conceptual schema

at the conceptual level to describe the structure and constraints for the whole database for a community of users. Uses a conceptual and or an implementation data model

external schema

at the external level to describe the various user views. Usually uses the same data model as the conceptual level

internal schema

at the internal level to describe physical storage structures and access paths. Typically uses a physical data model

menu-based interfaces forms-based interfaces graphical-based interfaces natural language interfaces interfaces for parametric users interfaces for the DBA combination of the above

Types of user interfaces for DBMS:

DDL (Data Definition Language)

Used by the DBA and database designers to define the conceptual schema of a database. In many DBMSs, it is also used to define internal and external schemas

DML (Data Manipulation Language)

Used to specify database retrievals and updates.

there is no access when the network connection to server is down and when the server malfunctions

What are the advantages of client-based applications over server-based applications?

-Which data to retrieve not how to retrieve data. -Mismatch between data structure in databases and data structure in C or C++ languages.

List at least two reasons why database systems support data manipulation using a declarative query language such as SQL, instead of just providing a library of C or C++ functions to carry out data manipulation.

A general purpose database manager (DBM) has five responsibilities: Øinteraction with the file manager. Øintegrity enforcement. Øsecurity enforcement. Øbackup and recovery. Øconcurrency control.

List five responsibilities of a database management system.

-Lack of independence from application programs. -Programs for manipulations of each file are needed. -Storage Redundancy. -Information inconsistency.

List four significant differences between a file-processing system and a DBMS.

B

A data dictionary can be used to... a)Schedule tasks in projects b)Record the database structure c)Encrypt the data d)Monitor performance

C

A description of the structure of a database is called... A) Outline B) Skeleton C) Schema D) View

A

Faster development of new applications is often possible in a database environment because... a)No file creation phase is needed b)New applications are independent of old ones c)No program planning is required d)The database administrator does all the programming

loading backing up reorganizing database file structures report generation performance monitoring other functions

Database system utilities:

-The capacity to change the internal schema without having to change the conceptual schema. -The capacity to change the conceptual schema without having to change the external schema and their application programs.

Explain the difference between physical and logical data independence.

-To create the scheme definition -To define the storage structure and access methods - To modify the scheme and/or physical organization when necessary - To grant authorization for data access - To specify integrity constraints

Five main functions of a database administrator are:

user interface

GUI screens that facilitates end user accessing the system to generate various reports from the content of database

B

In the object-oriented model, one important difference between program objects and database objects is that... a)Database objects are encapsulated b)Database objects persist c)Database objects have identifiers d)Database objects have state and behavior

efficient division of labor vertical and horizontal scaling of resources ability to use familiar tools on client side client access to remote data full DBMS functionality provided to client workstations overall better system price/performance

What are the advantages of client/server architecture?

data model operations

Operations for specifying database retrievals and updates by referring to the concepts of the data model

client server definition

Server accepts requests for data from the client and returns the results to the client

SDL (Storage Definition Language)

Specifies the internal schema

C

The middle level of the three-level database architecture, containing the entire information structure as seen by the DBA is the... a)External b)Internal c)Logical d)Physical

C

changing the schema to satisfy new data needs is called... A) prototyping B) system cycling C) schema evolution D) schema intension

centralized database management system

combine everything into single system including DBMS software, application programs and user interface processing software.

single-user systems

desk-top unit, single user, usually has only one CPU and one or two hard disks; the operating system may support only one user

multi-tier architecture

e-commerce system architecture in which the Web server is linked to a middle-tier layer that typically includes a series of application servers that perform specific tasks as well as to a backend layer of existing corporate systems

database schema

the description of a database. It includes descriptions of the database structures and the constraints that should hold on the database

VDL (View Definition Language)

for the External schema

logical/internal mapping

gives the correspondence between logical level and objects and their internal representations.

external/logical mapping

gives the corresponding between objects in user views and objects in the logical model

database instance

instances are created during data updates ad changes

two-tier architecture

it physically separates the user interface from the data management

Three-tier architecture

it separates the user interface, application logic, and data

multi-user systems

more disks, more memory, a multi-user operating system, and multiple CPUs. Serve a large number of users who are connected to the system via terminals. Often called server systems.

distributed database system

network allows the use of multiple computers

active data dictionary

used by DBMS software and users/DBA

passive data dictionary

used only by users/DBA

data dictionary

used to store schema descriptions and other information such as design decisions, application program descriptions, user information, usage standards, etc.

physical data model

provides concepts that describe details of how data is stored in the computer describe how data is stored as files in the computer by representing information such as record formats, record orderings, and access path

implementation data model

provides concepts that fall between conceptual and physical data models, balancing user views with some computer storage details

conceptual data model

provides the concepts that are close to the way many users perceive data

one-tier architecture

server handles all functionality

logical data independence

the capacity to change the conceptual schema without having to change the external schema and their application programs

physical data independence

the capacity to change the internal schema without having to change the conceptual schema