Centralized and Client/Server Architecture and Classification of DBMS Database Systems Lecture 7 Centralized and Client/Server Architecture and Classification of DBMS Database Management Systems Toqir Ahmad Rana

Today’s agenda Centralized and Client/Server Architecture for DBMS Database Management Systems Toqir Ahmad Rana Today’s agenda Centralized and Client/Server Architecture for DBMS Basic client/server architecture Two –tier client/server architecture Three –tier client/server architecture Classification of DBMS

Centralized and Client-Server Architectures Database Management Systems Toqir Ahmad Rana Centralized and Client-Server Architectures Centralized DBMS: combines everything into single system including- DBMS software, hardware, application programs and user interface processing software.

A physical centralized architecture. Database Management Systems Toqir Ahmad Rana A physical centralized architecture.

Basic Client-Server Architectures Database Management Systems Toqir Ahmad Rana Basic Client-Server Architectures Specialized Servers with Specialized functions Clients DBMS Server

Specialized Servers with Specialized functions: Database Management Systems Toqir Ahmad Rana Specialized Servers with Specialized functions: File Servers Printer Servers Web Servers E-mail Servers

Database Management Systems Toqir Ahmad Rana Clients: Provide appropriate interfaces and a client- version of the system to access and utilize the server resources. Clients maybe diskless machines or PCs or Workstations with disks with only the client software installed. Connected to the servers via some form of a network. (LAN: local area network, wireless network, etc.)

Logical two-tier client/server architecture Database Management Systems Toqir Ahmad Rana Logical two-tier client/server architecture

Database Management Systems Toqir Ahmad Rana DBMS Server Provides database query and transaction services to the clients Sometimes called query and transaction servers

Physical two-tier client-server architecture. Database Management Systems Toqir Ahmad Rana Physical two-tier client-server architecture.

Two Tier Client-Server Architecture Database Management Systems Toqir Ahmad Rana Two Tier Client-Server Architecture User Interface Programs and Application Programs run on the client side Interface called ODBC (Open Database Connectivity ) provides an Application program interface (API) allow client side programs to call the DBMS. Most DBMS vendors provide ODBC drivers.

Two Tier Client-Server Architecture Database Management Systems Toqir Ahmad Rana Two Tier Client-Server Architecture A client program may connect to several DBMSs. Other variations of clients are possible: e.g., in some DBMSs, more functionality is transferred to clients including data dictionary functions, optimization and recovery across multiple servers, etc. In such situations the server may be called the Data Server.

Three Tier Client-Server Architecture Database Management Systems Toqir Ahmad Rana Three Tier Client-Server Architecture Common for Web applications Intermediate Layer called Application Server or Web Server: stores the web connectivity software and the rules and business logic (constraints) part of the application used to access the right amount of data from the database server acts like a conduit for sending partially processed data between the database server and the client. Additional Features- Security: encrypt the data at the server before transmission decrypt data at the client

Logical three-tier client/server architecture. Database Management Systems Toqir Ahmad Rana Logical three-tier client/server architecture.

Classification of DBMSs Database Management Systems Toqir Ahmad Rana Classification of DBMSs Several criteria are normally used to classify DBMSs. Data model Number of users Number of sites Cost Types of access path

Database Management Systems Toqir Ahmad Rana Data Model Relational model represents a database as a collection of tables, where each table can be stored as a separate file. Object model defines a database in terms of objects, their properties, and their operations. Relational DBMSs have been extending their models to incorporate object database concepts and other capabilities; Object-relational model Hierarchical model represents data as record types and also represents a limited type of l:N relationship, called a set type. Network model represents data as hierarchical tree structures.

The schema of Figure 2.1 in network model notation Database Management Systems Toqir Ahmad Rana The schema of Figure 2.1 in network model notation

Database Management Systems Toqir Ahmad Rana Number of users Single-user systems support only one user at a time and are mostly used with personal computers. Multiuser systems, which include the majority of DBMSs, support multiple users concurrently.

Database Management Systems Toqir Ahmad Rana Number of sites A DBMS is centralized if the data is stored at a single computer site. A distributed DBMS (DDBMS) can have the actual database and DBMS software distributed over many sites, connected by a computer network. Homogeneous Heterogeneous Federated or Multidatabase Systems

Types of the access path Database Management Systems Toqir Ahmad Rana Types of the access path One well-known family of DBMSs is based on inverted file structures. Finally, a DBMS can be general purpose or special purpose. Online transaction processing (OLTP) systems,