Transcript Materialy/32/Lectures ClientServer

Slovak University of Technology
Faculty of Material Science and Technology in Trnava
Information Systems
Development
Basic architectures.
Mainframe architecture.
 With mainframe software architectures all intelligence is within
the central host computer.
 Users interact with the host through a terminal that captures keystrokes
and sends that information to the host.
 Mainframe software architectures are not tied to a hardware platform.
 User interaction can be done using PCs and UNIX workstations.
A limitation of architectures is that do not easily
support graphical user interfaces or access to multiple databases .
Basic architectures.
File sharing architecture.
 The original PC networks were based on file sharing architectures.
 The server downloads files from the shared location to PC.
 The requested user job is then run in the desktop environment.
 File sharing architectures work if shared usage is low, update contention is low,
 and the volume of data to be transferred is low.
 In the 1990s, PC LAN computing changed because the capacity of the
file sharing was strained as the number of online user grew
and graphical user interfaces (GUIs) became popular.
 PCs are now being used in client/server architectures
Basic architectures.
Client – Server architecture.
Main idea:
 data should be a processed in the place where they are stored
Advantages:
 restriction of data flow along the net
 restriction of data redundancy
 preservation of multi-user access
Base principle:
 dividing of powers between two processes, that works independent
Client – Server architecture.
Client process (front-end)
 process, which run on user Personal Computers
 main task is sending user requirements to database server and present
adequate results.
 process has no access to database, serves only as a intermediator
 server returns to client only a data, that are absolutely useful for next
processing.
Server process (back-end)
 process, which provide all database operations
 process can run on the same personal computer where runs a process
of client
 Process of server is also responsible for keeping of consistency, data
integrity and authorization of connecting users
Advantages:
 on the server site
Types of services
PRESENTATION RULES:
controls displaying of user information ( for example displaying of results,
menu, screen shots).
BUSINESS RULES (Logic): ensures application logic, operations which realize
application algorithms.
DATA RULES :
ensures manipulations with data in database - (SELECT, UPDATE…,
and transactional processing, ...)
FILES RULES : I/O operations
Two tier architectures.
 The user system is located in the user's PC environment and the DBMS
are usually in a server that is a more powerful machine that services many clients.
 Processing management is split between the user system
interface environment and the database management server environment.
 The database management server provides stored procedures and triggers.
TWO–TIER model
DATABASE SERVER
MIDDLEWARE
CLIENT
CLIENT
CLIENT
Variants of Two-tier architecture
Client-heavy
In client-heavy model the presentation rules and
business rules are on client side and data rules are on
relational database on server side.
It means the majority of processing is moved to client
side.
Variants of Two-tier architecture
Server heavy
In server-heavy model are business rules partially moved
to server side and presentation rules are staying on
clients PC.
Data rules, same as client-heavy, are located on server
side.
Two tier – server heavy
Client
Server
Database
Prezentation rules
Busines rules
Busines rules
Data rules
File rules
Three–Tier architectures
 In the three tier architecture, a middle tier was added
between the user system interface client environment
and the database management server environment.
 There are a variety of ways of implementing this middle
tier.
Three tier with an application server.
The three tier application server architecture allocates the main
body of an application to run on a shared host rather than in
the user system interface client environment.
The application server does not drive the GUIs; rather it shares
business logic, computations, and a data retrieval engine.
Advantages are that with less software on the client there is
less security to worry about, applications are more scalable,
and support and installation costs are less on a single server.
Three tier with an application server.
DATABASE SERVER
MIDDLEWARE
APPLICATION SERVER
MIDDLEWARE
CLIENT
CLIENT
CLIENT
Three tier with an application server.
Client
Application server
DB server
Database
Prezentation rules
Busines rules
Data rules
File rules
Distributed database systems.
Distributed database systems combine two technologies:
 Databases
 Communication
Distributed processing –
application works on one processor and database works on
another processor.
Distributed database is decomposed on several personal computers with
independent processors, but from user point of view there is
only one complex database.
There are three ways to distribute data:
I.
Fragmentation.
Different locations store different parts of the database.
Horizontal fragmentation stores different records on different servers.
Vertical fragmentation stores different fields on different servers.
This is good for when different sites need different data but must still
access data elsewhere.
II. Downloading.
A location will take a snapshot of the database parts it
needs and work off of that. This is good for times when the same data
must be local at different sites but does not change often.
III. Replication.
A location will keep a replicated copy of the database parts
it needs and work off of that. Replication ensures that all replicates
automatically and immediately update all other replicates of the
same part.
This is good for times when the same data must be local at
different sites and stay current.
Replications.
Replaication provides to users local actualized copy of data,
that could be added to original data.
It allows cheaper access to distributed continuos data processing.
The place from where are inicialized changes is called – publisher.
The place which receive changed replicated databse is - subscriber.
Replications.
place 1
place 2
primary copy
replica
place 3
replica
replica
place 4
place 1
place 2
replica
replica
replica
replica
place 3
place 4
There exists some rules for distributed databases:
A. Local autonomy. Each server in the distributed database should be independent
and have control of its data.
B. No reliance on a central site. A distributed database should not rely on a single
site for its operation.
C. Continuous operation. The entire distributed database should not have to
shutdown for maintenance.
D. Location transparency and location independence. User on the distributed
database should not concern itself with the location of data it needs.
E. Fragmentation independence. An application or user on the distributed database
should not concern itself if a table becomes fragmented over several servers.
F. Replication independence. An application or user on the distributed database
should not concern itself with the replication of data.
G. Distributed query processing. Each server in the distributed database should be
aware of how data is distributed for querying purposes.
H. Distributed transaction management. A distributed database should be able to
handle transactions involving multiple servers.
I. Hardware independence. It should not matter what hardware is used for servers
on the distributed database.
J. Operating system independence. It should not matter what operating system is
used for servers on the distributed database.
K. Network independence. It should not matter what network protocols are used
on the distributed database.
L. DBMS independence. It should not matter what DataBase Management Systems
are running on each server in the distributed database.
Classification of information demands
1. Operational level
- Here is a needs for every days system operations (accounting, store,
orders, invoices, salary, ...)
- Applications works through the „ad hoc“ transactions.
- Processing is called OLTP – On-Line Transaction Processing
- Databases on this level are called operational
Classification of information demands
2.
Dispositional level
- This level is superset to operational level
- database contains additionally also time horizon, various
accumulations and aggregations
- Serve for management decision and planning
- Processing on this level is called OLAP – On-Line Analytical Processing
- Users only read data on this level !
Classification of IS
A. - Transaction Processing Systems - TPS
-
Transaction Processing System (TPS) is a type of information systems.
TPS collect, store, modify, and retrieve the transactions of an organization.
-
A transaction is an event that generates or modifies data that is eventually
stored in an information system.
Classification of IS
Features of Transaction Processing Systems:

Rapid Response
Fast performance with a rapid response time is critical. Businesses cannot afford
to have customers waiting for a TPS to respond.
 Reliability
Many organisations rely heavily on their TPS; a breakdown will disrupt
operations or even stop the business.
 Inflexibility
A TPS wants every transaction to be processed in the same way regardless of the
user, the customer or the time for day.

Controlled processing
The processing in a TPS must support an organisation's operations.
Classification of IS
B. - Management Information Systems - MIS
-
The main task is deliver various reports and aggregated arrangements
according to different time, space and other point of view.
- Input information are data from transactional systems.
- Management Information Systems incorporate between ERP - Enterprise
Resource Planning.
Classification of IS
C. – Decision-Support Systems - DSS
- Decision-Support Systems are extension to MIS.
- DSS serves for various analysis and their using in the decision process.
- Above data there works a lot of DSS tools : software for data analysis ,
reports generator which are optimized for quick decision in the time and
many visualization tools.
Classification of IS
D.– Executive Information Systems – EIS
-
Executive Information Systems roof all previous.
-
EIS serves for obtaining of strategic decision information in financial
and personal area.
- New term is Business Intelligence, - here is included MIS, DSS and
also EIS.
-
EIS and DSS in early versions is possible to consider for predecesor
Data Warehouse and OLAP.
DW + OLAP
Top management
Middle level management DSS EIS
Dispositional
level
Marketing
MIS
Operation
Operational
OLTP
level
Information systems security.
Attacks
IS
Attacks
weak
places
Attacks
Information systems security.
Methods to achieve information systems security:
A. EBIOS (Expression of Needs and Identification of Security Objectives)
The EBIOS method is used to assess and treat risks relating to
information systems security (ISS).
It can also be used to communicate this information within the organisation
and to partners, and therefore assists in the ISS risk management process.
Reference frame EBIOS is composed of a set of tools to discover,
train or employ the method, and to contribute to its community development.
Information systems security.
B. PSSI (Information Systems Security Policy)
IS Security Policy reflects the strategic vision of the management
team of an organisation such as an SME, industrial group or government
agency in the ISS field.
The main purpose of this guide is to provide ISS managers with a
framework for preparing an information systems security policy
in their organisation.
Information systems security.
The information systems security policy guide is divided into four sections:
- the introduction - sets out the role of the information systems
security policy in relation to the organisation's standards baseline and describes the
basis from which it derives its legitimacy;
- the methodology contains a detailed description of the approach for conducting a
project to develop an information systems security policy, and gives
recommendations for devising security rules;
- the security principles baseline;
- a list of ISS reference documents (evaluation criteria, statutory texts, standards,
codes of ethics, supplementary reports, etc.).
Information systems security.
C. TDBSSI (Information Systems Security Trend Chart)
An ISS trend chart is a management tool used at various levels of decision-making,
management, and operations to provide an analytical overview of the security
situation, from both a technical and functional viewpoint (showing risk coverage,
quality of security policy, follow-up of audits, actions, and alerts, etc.).
A trend chart is an essential graphical tool that provides analytical information for
use in monitoring all actions involving information systems security. It helps ensure
that the strategy defined in the security policy is implemented at management
and operational levels, and that all significant information is relayed to
decision-makers.