basic of system architecture

Me :  Hi, pooja ! How are you ???

Pooja : hey...hi...i am good , i was about to call you today . I need your help.

Me : Yeah sure.. tell me, what happened ??

Pooja : From next Monday my 2nd semester of college is starting so before that i want to study the basics of  SYSTEM ARCHITECTURE.But i didn't get any tutor for it so as you are my senior...can you help me out.

Me : yeah sure,i have already studied this subject last year.

Pooja : Thats wonder full...shall we start right now.

Me: Yeah sure but Before starting the architecture you need to be aware of some terms which would be used frequently.

MAINFRAME COMPUTERS- A large high speed computer, especially one supporting numerous work  station. The CPU and primary memory of computer.

Pooja : yeah, i have seen it in ma college , it is still there just for show.

Me : yeah ,that's the one i am talking about,

Pooja :okie, what next .

Me : yeah...There is data base application , which is divided into three distinct components.

1) DATABASE SERVICE- This is the back end database server and the data that resides in the data base.

2) APPLICATION SERVICE-This is the application or business logic that manipulates the data that is                       retrieved from database.

3) PRESENTATION SERVICE- This is the user interface.The presentation services must be able to manipulate the data into an understandable form.

Me- And there is a another term.... MIDDLE WARE

MIDDLE WARE- Software that function as a conversion or translation layer,whose task is to ensure that software from a variety of source will work together correctly.

Pooja- ohh...i got it, but what's the use of it.

Me- yeah...i am just coming to those points.

SYSTEM ARCHITECTURE -It establishes the basic structure of the system,which can be classify as 1tier ,2 tier and 3 tier (multi tier) architecture

1 tier- Here the central computer served the whole business community  and was accessed by dumb terminals. All processing take place at single computer.It is simple, efficient but least secure and very costly to run. Difficult to handle when multiple user try to edit any program.

2 tier -2 Tier architecture is also called as client /server model.The client sitting on the personal computer will request for data to the server .Here the user interface and the application services tend to get mixed together.Client may require a lot of resource like memory.disk etc.When the application connects the data service and request the data.The server just returned the data requested.

                        

3 tier - In this tier all the three services i.e data, application(middle tier) and presentation(client tier) are separated.

Me :I have already told you about these layer above, Now you will  see their use. 

   

And here we will use MIDDLE WARE  which we have discussed above. Middleware is a kind of software that links programs running on different platforms, transmitting messages and data. It plays an important role in 3-tier architecture. There are two types of middlewares: the first connects client programs to server programs, and the second provides data access connections to heterogeneous data sources. 

Pooja : Ohhh....they are named according to there use .

Me : Yeah, exactly , You can also visualize these three logical tiers correspond to physical separation between different type of devices.

                                

                                a)Database server (often an RDBMS or Relational Database)

                                b)Web server or application server

                                c)Browser or GUI Application.

Here, first the client sends a request to database server which responds back and sends the result to application server for processing. Finally, application server responds back to client on its browser or GUI.
Advantage of this tier is - Removes a huge process burden from  client machine

                                       Reduces data replication

Pooja- Ohh....vov things are very clear now. 

Me- Yeah. you can relate these tier practically and they are easy to understand. Hope you understood all things clearly.

Me : There is one more thing which is very important according to the current scenario .

Pooja : What is it ?

Me : Internet. Using an internet server.As everything is on the web now , 3 tier is often used to refer to websites.A middle dynamic content processing application server. A back end database comprising of DBMS and RDBMS.

But you have to take care of the virus , threats and malware that comes handy with it. So u make sure to additionalize your tier with a firewall server so as to block all threats and for better security.

Pooja : It was a great session. Got a clear view of everything before hand.

Pooja- Thanks a ton for helping me out.

Me- Your welcome. If you face any query feel free to call me. Best of luck for your new session .

Pooja- Thank you .