This document discusses data models and database management system architectures. It covers: 1) Categories of data models including conceptual, implementation, and physical models. 2) Classifications of DBMSs including the data model used (relational, network, etc.), number of users, number of sites, and cost. 3) Common multi-user DBMS architectures like teleprocessing, file-server, and client-server (two-tier and three-tier).

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Dr Ramadan Babers
Faculty of Science - Helwan University
Fall 2018
D B
LEC-05

2. 1- Data Model
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 A collection of concepts that can be used to define
the DB structure (data items& types, relationships,
operations, behavior, and constraints).
 Some Data Models:
 Entity Relationship model
 Relational Model
 hierarchical & network models
 object-data models

3. 2- The role of data models
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4. 3- Categories of Data Models
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 Conceptual (high-level, semantic) data models:
 Provide concepts that are close to the way many users
perceive data.
 (Also called entity-based or object-based data
models.)
 Implementation (representational) data models:
 Provide concepts that fall between the above and below,
used by many commercial DBMS implementations (e.g.
relational data models used in many commercial
systems).
 Physical (low-level, internal) data models:
 Provide concepts that describe details of how data is
stored in the computer. These are usually specified in an
ad-hoc manner through DBMS design and
administration manuals

5. 3- Categories of Data Models (cont.)
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6. 4- Classification of DBMSs
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 Data Model Classification
 relational,
 network,
 hierarchical,
 object-oriented
 Number of users
 single user or multi-user
 Number of Sites
 centralized vs distributed
 Cost of the DBMS
Data Model
Number of
users
Number of
sites
Cost of the
DBMS

7. 5- System Catalog
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 Repository of information (metadata) describing
the data in the database.
 One of the fundamental components of DBMS.
 Typically stores:
 names, types, and sizes of data items;
 constraints on the data;
 names of authorized users;
 data items accessible by a user and the type of access;
 usage statistics.

8. 6- Multi-User DBMS Architectures
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1- Teleprocessing
2- File-server
3- Client-server
A- Two-Tier
B- Three-Tier

9. 6-1 Teleprocessing
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 Traditional architecture.
 Single mainframe with a
number of terminals
attached.
Mainframe
Terminals

10. 6-2 File-Server
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 File-server is connected to several
workstations across a network.
 Database resides on file-server.
 DBMS and applications run on each workstation.
 Disadvantages include:
 Significant network traffic.
 Copy of DBMS on each workstation.
 Concurrency, recovery and integrity control more complex.

11. 6-2 File-Server Architecture (cont.)
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DBMS &
Applications
Database
resides on
file-server

12. 6-3 Client-Server
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A- Traditional Two-Tier
 Client (tier 1) manages user interface and runs
applications.
 Server (tier 2) holds database and DBMS.
 Advantages include:
 wider access to existing databases;
 increased performance;
 possible reduction in hardware costs;
 reduction in communication costs;
 increased consistency.

13. 13
Traditional
Two-Tier
Client-Server
6-3 Client-Server (cont.)
Tier-2
Database &
DBMS
Tier-1
User interface
& applications

14. 14
6-3 Client-Server (cont.)

15. 15
B- Three-Tier
 Client side presented two problems preventing
true scalability:
 ‘Fat’ client, requiring considerable resources on client’s
computer to run effectively.
 Significant client side administration overhead.
 By 1995, three layers proposed, each
potentially running on a different platform.
6-3 Client-Server (cont.)

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 Advantages:
‘Thin’ client, requiring less expensive hardware.
Application maintenance centralized.
Easier to modify or replace onetier without
affecting others.
Separating business logic from database functions
makes it easier to implement load balancing.
6-3 Client-Server (cont.)

17. Three-Tier Client-Server
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6-3 Client-Server (cont.)

18. 7- Transaction Processing Monitors
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 Program that controls data transfer
between clients and servers in order to
provide a consistent environment,
particularly for Online Transaction
Processing (OLTP).
 Online Analytical Processing (OLAP).

19. TPM as middle tier of 3-tier client-server
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