Introduction of current trends - centralised and client srver bca dbms unit 5

Introduction of current trends – centralised and client server architecture

Most of the Net Applications use the Client-Server architecture, which refers to two processes or two applications that communicate with each other to exchange some information. One of the two processes acts as a client process, and another process acts as a server.

Client Process

This is the process, which typically makes a request for information. After getting the response, this process may terminate or may do some other processing.

Example, Internet Browser works as a client application, which sends a request to the Web Server to get one HTML webpage.

Server Process

This is the process which takes a request from the clients. After getting a request from the client, this process will perform the required processing, gather the requested information, and send it to the requestor client. Once done, it becomes ready to serve another client. Server processes are always alert and ready to serve incoming requests.

Example − Web Server keeps waiting for requests from Internet Browsers and as soon as it gets any request from a browser, it picks up a requested HTML page and sends it back to that Browser.

Note that the client needs to know the address of the server, but the server does not need to know the address or even the existence of the client prior to the connection being established. Once a connection is established, both sides can send and receive information.

2-tier and 3-tier architectures

There are two types of client-server architectures −

2-tier architecture − In this architecture, the client directly interacts with the server. This type of architecture may have some security holes and performance problems. Internet Explorer and Web Server work on two-tier architecture. Here security problems are resolved using Secure Socket Layer (SSL).

3-tier architectures − In this architecture, one more software sits in between the client and the server. This middle software is called ‘middleware’. Middleware are used to perform all the security checks and load balancing in case of heavy load. A middleware takes all requests from the client and after performing the required authentication, it passes that request to the server. Then the server does the required processing and sends the response back to the middleware and finally the middleware passes this response back to the client. If you want to implement a 3-tier architecture, then you can keep any middleware like Web Logic or WebSphere software in between your Web Server and Web Browser.

                  Or

Database management in centralized, file server architecture

March 2, 2013 by Admin Leave a Comment

Database management in centralized database architecture: In centralized database architecture, data, application programs and DBMS is located in a mainframe system. An application program is used for taking inputs from users and displaying it to the screen. It also communicates with DBMS using SQL. It is used in DB2 and SQL/DS databases.

Working: When a user sends a SQL query from computer system, it is received by DBMS (database management system). Then the request is processed by the DBMS. It also communicates with the database to generate a result. After that it communicates with the application program and the result is displayed in the screen of the user.

Disadvantage of database management in centralized database architecture: When more users are added to the system, the load to the system increases and it decreases the performance of the overall system.

Database management in file server architecture: A file server is used to share files in a server. In file server architecture, data can be accessed by computer systems. This data is located in file server. To access data networking software is used by file server. In this architecture a copy of DBMS is created for each user. This architecture works well if users have to retrieve simple data comprising of few rows and columns from the database. It is used in dBASE and Microsoft Access database.

Disadvantage of database management in file server architecture: Since every time a database scan is made, network traffic is increased and performance is decreased.