[Music] hello everyone and welcome back in this video we are going to discuss about the dbms architecture let us first discuss the centralized dbms architecture this is a diagram that shows the physical components of a centralized architecture in earlier architectures mainframe computers were used to process all the system functions and the reason for that was users accessed systems via computer terminals that provided only display capabilities but no processing capabilities that is the computer terminals used by the users were not capable of processing but it was only capable of displaying any information to the user so all the processing were performed remotely on the computer system and only the display information was sent to the computer terminals and these terminals were connected to the computer system via a network now as the prices of hardware started to decline or reduce the terminals were replaced by personal computers and workstations initially database systems used these computers in a similar way as the display terminals but the dbms was centralized where all the functionalities of the dbms user processing and execution of the application program all were done on one machine so all the processing were done over here and the display information was sent to the display terminals via our network slowly dbms systems started making use of the processing ability of the systems at the user side also and not just at the server side and this led to client server architecture so this is about the centralized dbms architecture now let's look at the basic client server architectures first we're going to see a general overview of a client server architecture and then we will see how it applies to dbms this client server architecture was developed to deal with large number of personal computers workstations printers file servers etc all connected via a network the idea behind that or the goal was to define specialized servers with specific functionalities like for example we can connect a number of personal computers to file servers and these file servers are responsible for maintaining the files of the client machines another machine can be designated as a printer server and this machine can be connected to various printers and all the print requests from the client are forwarded to this machine so that way we have different specialized servers with specific functionalities and the resources each of these servers provides can be accessed by the client machines the client machines provides the users with appropriate interfaces to utilize these servers this diagram illustrates the client server architecture at the logical level and this diagram illustrates the client server architecture at the physical level a client is usually a user machine that provides user interface capabilities and local processing that is just as i said the client to machine provides the users with appropriate interfaces to utilize these servers so when a client requires access to any additional functionality that does not exist in its machine it connects to a server that provides the necessary functionality as required by the user a server is a machine that provides services to the client machines like access to the files printing or access to the database etc now the two main types of basic client server architectures are the two tire and the three tire client server architectures which we will be discussing now so first let us discuss the two tire client server architectures initially the rdbms started as a centralized system then later when the client server architecture started getting incorporated into many of the commercial dbms at that time the user interfaces and application programs moved to the client side and the query and transaction functionality remained on the server side and such a server is called the query server or transaction server because it provides these two functionalities in rdbms the server is also called the sql server because most of the rdbms servers are based on the sql language and standard now when dpms access is required the application program establishes a connection with the dbms or the server side open database connectivity or odbc provides an application programming interface or an api that allows programs from the client side to call the dbms on the server side that way a client program can connect to several rdbms and send query and transaction requests using odbc api and these requests sent by the client programs are processed at the server sides so this odbc api is used to establish a connection between the client and the server so once the connection is established the client program can communicate with the dbms on the server side a similar standard for java programming language is also defined and it is called jdbc that is java database connectivity and jdbc allows the java client programs to access the dbms which is on the server side the advantages of two tyre architectures are the first one is simplicity and the second one is its compatibility with other systems the emergence of world wide web or www changed the roles of clients and server thus leading to three tyre architecture so this is all about the two tyre client server architectures and it is called two tire because its software components are distributed over two systems the client and the server next let us look at the three tire client server architectures many web applications use this three tire architectures and it is called a three-tier architecture because it has an additional intermediate layer between the client and the database server the intermediate layer is sometimes called the application server or sometimes called the web server based on the application now this application server or web server stores rules used to access data from the database server this intermediate layer accepts requests from the client processes the requests and sends database commands to the database server and then this intermediate layer acts as a channel for passing the process data from the database server to the client here the data can be processed further and filtered to make it presentable to the users in the graphical user interface or the gui format so that is all about the three tire client server architectures where the user interface the application rules and the data access act as the three tires with this we come to the end of this video we discussed about the centralized dbms architecture as well as the client server architectures in that we have the two tire architecture and the three tire architecture hope you have understood these concepts thank you [Music] you