Database Management System Contents Client Server Architecture AdvantagesDisadvantages

Database Management System Contents Client Server Architecture Advantages/Disadvantages of C/S Architecture Types of C/S Architecture Distributed Database Homogenous and Heterogeneous Distributed Database

Client Server Architecture • • • Client/server architecture is a computing model in which the server hosts, delivers and manages most of the resources and services to be consumed by the client. This architecture has generally two types of logical components – Client and Server that share computing resources. Client/server architecture may also be referred to as a networking computing model because all the requests and services are delivered over a network. Client are generally personal computers or any device at the user end that can send requests over network. Server is a powerful computer that can store and process large amount of data and requests. Generally server is called Backend and client is called Frontend.

Client Server Architecture • • • The application software and tools to communicate with database reside on client side and are used to generate requests for data. E. G. Browsers. DBMS runs on Server side that receives and process the client requests for data.

Client Server Architecture Advantages of C/S Architecture ◦ ◦ ◦ ◦ ◦ Scalable. Easier Data Sharing. Client Independence. Effective Network load Data integrity. Centralized Management Cost Effective Sensible Allocation of Resources Physical Data Independence Minimize Data Redundancy

Client Server Architecture Disadvantages of C/S Architecture ◦ ◦ Expensive Needs Technical Skills Complex Difficult to maintain

Client Server Architecture Types of C/S Architecture Client- Server Architecture can be classified into four types. ◦ ◦ Single-Tier Architecture Two-Tier Architecture Three-Tier Architecture N-Tier Architecture

Client Server Architecture Single-Tier C/S Architecture This architecture contains only one system. The system acts as both client and server. This architecture is used where the size of the database is minimum. So the system stores both database and applications to access it. Dumb terminals are used to access the database.

Client Server Architecture Single-Tier C/S Architecture Advantages: ◦ ◦ ◦ Financially feasible. Easier to install and maintain. No need of strong technical background. Disadvantages: ◦ Not Scalable. ◦ No Data Sharing

Client Server Architecture Two-Tier C/S Architecture • • This is the basic Client Server Architecture with both client and server that share computing resources. Client are generally personal computers or any device at the user end that can send requests over network without any intermediate. Server is a powerful computer that can store and process large amount of data and requests.

Client Server Architecture Two-Tier C/S Architecture Advantages: ◦ ◦ ◦ Easiest model of C/S Architecture. User Friendly. Consistent connection between user and database Data Sharing. Flexible and scalable. Disadvantages: ◦ Expensive than single-tier architecture. ◦ Requires reliable network.

Client Server Architecture Three-Tier C/S Architecture A 3 -tier architecture separates its tiers from each other based on the complexity of the users and how they use the data present in the database. It is the most widely used architecture to design a DBMS.

Client Server Architecture Three-Tier C/S Architecture User (Presentation) Tier − End-users operate on this tier and they know nothing about any existence of the database beyond this layer. At this layer, multiple views of the database can be provided by the application. All views are generated by applications that reside in the application tier. Application (Middle) Tier − At this tier reside the application server and the programs that access the database. For a user, this application tier presents an abstracted view of the database. Endusers are unaware of any existence of the database beyond the application. At the other end, the database tier is not aware of any other user beyond the application tier. Hence, the application layer sits in the middle and acts as a mediator between the end-user and the database. Database (Data) Tier − At this tier, the database resides along with its query processing languages. We also have the relations that define the data and their constraints at this level.

Client Server Architecture Three-Tier C/S Architecture Advantages: ◦ ◦ ◦ ◦ ◦ Scalable as Database needs to connect only Middle tier not every client Data Integrity and security Improvement Distinction between user control and database control Load Balancing. Economic Clients Easier modification and maintenance. Disadvantages: Extremely Complex. Requires reliable network. Comparatively slower than other models.

Client Server Architecture N-Tier C/S Architecture Multitier architecture (often referred to as n-tier architecture) or multilayered architecture is a client–server architecture in which presentation, application processing, and data management functions are physically separated. The most widespread use of multitier architecture is the three-tier architecture. Theoretically there is no difference between 3 -Tier and N-Tier C/S Architecture. Some people refer to the N Tier Architecture where 'N' can be number of middleware. .

Client Server Architecture Distributed Database A distributed database is a database in which storage devices are not all attached to a common processor. Data is physically stored across multiple sites in multiple computers. ◦ ◦ ◦ Databases in the collection are logically interrelated with each other. Often they represent a single logical database. The processors in the sites are connected via a network. Data at each site is controlled by a separate DBMS which is further part of a global DBMS/application. Transparent- end user feels like working with a single computer. A special software DDBMS (Distributed Database Management System) manages the overall database.

Client Server Architecture Distributed Database

Client Server Architecture Distributed Database Advantages: ◦ ◦ ◦ ◦ Scalable. Fastest in DBMS architectures. User-Friendly. Processor Independent. Reliable. Load Balancing. Easier modification and maintenance. Disadvantages: ◦ Extremely Complex. ◦ Requires reliable network. ◦ Expensive.

Client Server Architecture Distributed Database can be classified into two types: ◦ Homogeneous Distributed Database: if in a Database all the sites use same DBMS then the overall database is called Homogeneous Distributed DBMS. All sites are aware of each other and can communicate with each other. This type of database is very flexible and scalable. Addition of new sites or removal of a site is very easy.

Client Server Architecture Distributed Database ◦ Heterogeneous Distributed Database: in this type of Database all the sites use different DBMS, different schema so query processor and transaction processing is difficult. Sites may not be aware of other sites. So co-ordination between them is minimum that leads to increased complexity.

Chapter End