https://youtu.be/yP14a2Qzx8c DATABASE PROTOCOLS OVERVIEW Oracle Two-Tier Two-Tier and Three-Tier Computing Models

1. Advanced Database Protocols
Prof. Hitesh Mohapatra

2. DATABASE PROTOCOLS OVERVIEW
Suppose that you have a database of customer
information that is accessed by customer service
personnel located throughout the country. You use
database to emulate the database server servicing many
requests for information.
A database can:
• Connect to the server
• Submit an SQL query
• Retrieve and process the information
• Disconnect from the server

3. PROTOCOLS
The following database protocols are supported:
• Oracle Two-Tier
• ODBC

4. Oracle9i Application Server Architecture
Oracle9i Application Server consists of a set of
services that can be implemented in a
distributed environment for scalability and
reliability. The following sections provide an
architectural overview of Oracle9i Application
Server.

5. Two-Tier and Three-Tier Computing
Models
• Client/server computing architectures are
commonly described as having two or more
tiers according to how application logic is
distributed between client and server.
Minimally, a client/server architecture must
have a client tier and a server tier. Oracle's
internet computing model is based on a multi-
tiered computing model in which
Oracle9i Application Server functions as a
middle tier, or application server tier.

6. Two-Tier Computing Model
• Traditional database client/server architecture is based on a
two-tier computing model. This model consists of a client
tier and a database server tier (see Figure 1-2).
• Processing tasks and application logic are shared between
the database server and the client.

7. Two-Tier Computing Model
Disadvantage..
• Several disadvantages exist for this model. The
clients in a two-tier computing model are fat
clients, where much of the processing power
and application logic reside. This makes the
clients costly to maintain.
• Furthermore, clients can be operating on
different platforms, necessitating the
deployment of platform-specific versions of
applications.

8. Three-Tier Computing Model
The three-tier computing model evolved to address the
problems of the two-tier model.
• In a three-tier model, a middle tier exists between
clients and the database server.
• This middle tier consists of an application server that
contains the bulk of the application logic.
• Clients in the model are thin clients. With this
architecture, application logic resides in a single tier
and can be maintained easily at one location.
• The architectural design of the middle tier is optimized
for server functions including access to a database.

9. Three-Tier architecture
In this three-tier architecture, the client software (the client tier) is lightweight enough to be downloaded on demand, and
does little but present the user interface for a server-side application. The bulk of the application logic is implemented
either in the application server or in the database.

10. ODBC
Open Database
Connectivity

11. What Is an ODBC Driver?
An ODBC driver uses the Open Database Connectivity
(ODBC) interface by Microsoft that allows applications to
access data in database management systems (DBMS)
using SQL as a standard for accessing the data.
ODBC is a standard which allows applications to import
data from any compliant database, without having to
understand the database file format or server protocol. In
fact, the ODBC architecture is quite straightforward and is
built on two tiers between an application and a database
from which it wants to import data.

12. ODBC Manager
• The heart of the ODBC architecture is a piece of
Microsoft software called the ‘ODBC manager’,
which is the central point of contact for an
application.
• An application can interrogate the ODBC manager
to find out what drivers and data sources are
installed on a machine, and use this information
to make connections to the required database.
• The ODBC manager handles the connection
request, and locates the appropriate ODBC driver
in order to establish the connection.

13. ODBC drivers
The driver software understands the file-format or server protocols relevant to the
corresponding database system, and is responsible for extracting the actual data.
ODBC architecture

14. Once an application has established an ODBC
connection to a database, it will extract data
through an SQL query. The benefits of ODBC are
two-fold:
• The application doesn’t need to know the
database file format or server protocol
• A common SQL grammar can be used with any
ODBC connection, regardless of the underlying
database format.