JDBC Architecture:

• The JDBC API supports both two-tier and three tier processing model for database access but in general, JDBC Architecture consist of two layers:
• 1. JDBC API: This API provides the Application-to-JDBC Manager connection.
• 2. JDBC Driver API: This supports  the JDBC Manager-to-driver Connection.
• The JDBC API uses a driver manager and database specific drivers to provide connectivity to database.
• The JDBC driver manager ensure that the Correct driver is used to access each data Source.
• The Driver manager is capable of supporting multiple concurrent drivers connected to multiple databases.

Two tier database design:

• The two-tier is based on Client-Server architecture.
• The direct Communication takes place between client and server.
• There is no mediator between client and server.
• In this type of Database design, User Interface and business Logic is in client side and Database is on server side.
• The client computer directly access the data without seeing the database. This means that the data on the server is much more secure.

Advantages:

• It is easy to implement.
• It is easy to maintain.
• It performs faster.
• High portability.

Disadvantages:

• Performance is reduced when clients increase.
• More suitable to small scale group and simple for Web-based.

Three tier database design:

• In this type of Database design, User interface is on client side, Business Logic is on separate application server and database is on Database Server.
• In three-tier database design, client communicates with database server through application server.
• Three-tier architecture typically have Presentation tier, Business tier or data access tier,  and data tier.
• Three layers in the three tier architecture are as follows:

         1. Client layer(Presentation layer)
         2. Business layer(Application layer/Middle layer)
         3. Data layer

Client layer:

• It is also called as presentation layer which contains UI part of our application.
• This layer is used for the design purpose where data is presented to the user or input is taken from the user.

Business layer:

• In this layer all business logic written like validation of data, calculation, data insertion etc.
• It acts as an interface between client layer and data layer.
• It is also called the mediator, helps to make communication faster between client and data layer.

Data layer:

• In this layer actual database is comes in the picture.
• It contains method to connect with database and to perform insert, update, delete, get data from database based on our input data.

Advantages:

• Improved security.
• Performance is higher than 2-tier.
• Easy to maintain and modification is bit easy.

Disadvantages:

• Increase Complexity.