# Database Architecture

The database architecture depends on the kind of system on which the database is running. There are different kinds of database architectures:

* **Centralized**\
  Both the data and the client accessing the data are at the site of the database system
* **Client-Server (two-tier/three-tier)**\
  One server machine executes the work on behalf of multiple client machines
* **Parallel**\
  The database system runs on multi-node and multi-core systems
* **Distributed**\
  This consists of multiple communicating database systems located at different geographical locations

The client-server architecture is most commonly used today, wherein clients remotely connect to the database system that runs on the server.

There are two kinds of client-server architecture:

![](/files/-M5-0_Ci5sTlkaUbP1fv)In the **two-tier** architecture, client programs communicate with the database over a network, using ODBC/JDBC/Embedded SQL.

In the **three-tier** architecture, client programs first communicate with an application server, which in-turn communicates with the database system. This is commonly used for web-based applications.


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