Data Architecture in DBMS
The DBMS
design depends upon its architecture. The basic client/server architecture is
used to deal with a large number of PCs, web servers, database servers and
other components that are connected with networks.
The
client/server architecture consists of many PCs and a workstation which are
connected via the network.
DBMS
architecture depends upon how users are connected to the database to get their
request done.
Types of DBMS Architecture
Database
architecture can be seen as a single tier or multi-tier. But logically,
database architecture is of two types like: 2-tier
architecture and 3-tier
architecture.
1-Tier
Architecture
o
In this
architecture, the database is directly available to the user. It means the user
can directly sit on the DBMS and uses it.
o
Any
changes done here will directly be done on the database itself. It doesn't
provide a handy tool for end users.
o
The 1-Tier
architecture is used for development of the local application, where
programmers can directly communicate with the database for the quick response.
2-Tier
Architecture
o
The 2-Tier
architecture is same as basic client-server. In the two-tier architecture,
applications on the client end can directly communicate with the database at
the server side. For this interaction, API's like: ODBC, JDBC are used.
o
The user
interfaces and application programs are run on the client-side.
o
The server
side is responsible to provide the functionalities like: query processing and
transaction management.
o
To
communicate with the DBMS, client-side application establishes a connection
with the server side.
3-Tier
Architecture
o
The 3-Tier
architecture contains another layer between the client and server. In this
architecture, client can't directly communicate with the server.
o
The
application on the client-end interacts with an application server which
further communicates with the database system.
o
End user
has no idea about the existence of the database beyond the application server.
The database also has no idea about any other user beyond the application.
o
The 3-Tier
architecture is used in case of large web application.
The design of a DBMS depends on its
architecture. It can be centralized or decentralized or hierarchical. The
architecture of a DBMS can be seen as either single tier or multi-tier. An
n-tier architecture divides the whole system into related but independent n modules,
which can be independently modified, altered, changed, or replaced.
In 1-tier architecture, the DBMS is the
only entity where the user directly sits on the DBMS and uses it. Any changes
done here will directly be done on the DBMS itself. It does not provide handy
tools for end-users. Database designers and programmers normally prefer to use
single-tier architecture.
If the architecture of DBMS is 2-tier,
then it must have an application through which the DBMS can be accessed.
Programmers use 2-tier architecture where they access the DBMS by means of an
application. Here the application tier is entirely independent of the database
in terms of operation, design, and programming.
3-tier
Architecture
A 3-tier architecture separates its
tiers from each other based on the complexity of the users and how they use the
data present in the database. It is the most widely used architecture to design
a DBMS.
·
Database
(Data) Tier − At
this tier, the database resides along with its query processing languages. We
also have the relations that define the data and their constraints at this level.
·
Application
(Middle) Tier − At
this tier reside the application server and the programs that access the
database. For a user, this application tier presents an abstracted view of the
database. End-users are unaware of any existence of the database beyond the
application. At the other end, the database tier is not aware of any other user
beyond the application tier. Hence, the application layer sits in the middle
and acts as a mediator between the end-user and the database.
·
User
(Presentation) Tier −
End-users operate on this tier and they know nothing about any existence of the
database beyond this layer. At this layer, multiple views of the database can
be provided by the application. All views are generated by applications that
reside in the application tier.
Multiple-tier database architecture is
highly modifiable, as almost all its components are independent and can be
changed independently.
Levels
in 3-tier Architecture
1. External Level (View Level) – It is relevant to each user
2. Conceptual Level (Logical Level) – It is what kind of data to be stored in database
and relationship among data.
(a) All entities, attributed and
their relationship
(b) Security and integrity.
3. Internal Level (Storage Level) – Physical representation of database how the data is
stored in database. It covers data structure and file organization.
No comments:
Post a Comment