Three Tier Client-Server Architecture

Posted by AJ × 06:32

• Common for Web applications

• Intermediate Layer called Application Server or Web Server:

• Stores the web connectivity software and the business logic part of the application used to access the corresponding data from the database server

• Acts like a conduit for sending partially processed data between the database server and the client.

• Three-tier Architecture Can Enhance Security:

• Database server only accessible via middle tier

• Clients cannot directly access database server

Classification of DBMSs

• Based on the data model used

• Traditional: Relational, Network, Hierarchical.

• Emerging: Object-oriented, Object-relational.

• Other classifications

• Single-user (typically used with personal computers) vs. multi-user (most DBMSs).

• Centralized (uses a single computer with one database) vs. distributed (uses multiple computers, multiple databases)

Variations of Distributed DBMSs (DDBMSs)

• Homogeneous DDBMS

• Heterogeneous DDBMS

• Federated or Multidatabase Systems

• Distributed Database Systems have now come to be known as client-server based database systems because:

• They do not support a totally distributed environment, but rather a set of database servers supporting a set of clients.

Cost considerations for DBMSs

• Cost Range: from free open-source systems to configurations costing millions of dollars

• Examples of free relational DBMSs: MySQL, PostgreSQL, others

All Syllabus