COM III MCA

Slide 1

COMPONENT BASED TECHNOLOGY

Multiprocessor OSIf the system workload cannot be handled satisfactory by the single processor.The response is to apply multiple processor to the problem.It provides increased reliability. An operating system capable of supporting more than one computer is called a multiprocessor OS.

Classes of operating systemThe OS for distributed computing can be network OS, distributed OS or middleware os.The distributed OS runs on multiple CPUs.It is managed as single system.It may be multi-processor / multi-computer based.

Difference between network vs distributed OSNetwork Os does not provides single image view for any of its services.Its goal is to offer services to its remote clients.All distribution of task is explicit to the user.It provides remote access services and file transfer.Sharing is provided with networks.

The advantage of the network is its scalability and distributed is transparency.Middleware is added on top of network OS to combine the advantages of distributed and network OS.

Distributed object systemObject oriented software development makes software suitable for change.In distributed object model, objects are distributed throughout the network.To allow communication, message passing is used.

Advantages of distributed object systemFacilitate rapid application development.Reduce the time and cost of software development.Higher degree of system integrationCapability to extend and scale the systemRapid evolution of projectsSupport reusable and business components.

Functionalities of distributed object system

Object REGISTERYClient ObjectServer ObjectClient ProxyServer proxyRuntime supportNetwork subsystemNETWORK

Object registry: It facilitates distributed objects to be registered.It is a program that runs on the serverIt contains the list of all remote objects that the server is prepared to export.To access the distributed object, the object client looks up the registry for obtaining a reference to the object.Network support: It provides the physical connection between the client and server machines

Client proxyIt handles the call to the remote object.Converts the data into format understood by heterogeneous client and server.Run time environment:It is responsible for interprocessor communication.Sending the message to the server side.The server side receives the message and forward the call. Server proxy It receives the call from the run time environment and converts the data to local. It rearrange the method call into a format understand by server object.

Multi tier architectureClient server computing is a managerial and computational model.It partition the work to maximize the flexibility and efficiency.The need for the multiple users and GUI presentation format has led to the evolution of client server architecture in the form of two-tier approach.

ofclient/serverarchitecture, you need to determine if it will be theclientor theserverthat handles the bulk of the workload.

The client server architecture in the form of layers asPresentation logic (user)Business logicDatabase serverIn 1-tier architecture layers present in same machine.

The two-tier is based on Client Server architecture. The two-tier architecture is like client server application. The direct communication takes place between client and server. There is no intermediate between client and server. Because of tight coupling a 2 tiered application will run faster.

Two-tier architecture

The user interface and business logic or located on the client side.The database management services are located on the server.The client is known as fat client because the business logic is located on the client side.

Advantage of 2-tier architectureIt is scalable upto 100 clients.It improves usability by supporting a user friendly interface.It allows data to be shared.The server can act as client for another server.Used in less complicated, non-time critical information processing.

DisadvantageThe performance decrease when the number of user exceeds 100.The usage of database software reduces flexibility.Processing overhead on the client side.Not suitable for batch processing jobs.There is a need for the separation of business logic from the presentation interface.

Three-tier architectureThe limitation of two-tier architecture can be overcome by including a middle tier.Between the client and database tier.Tier 1:(User Interface Tier)The client contains the presentation logic, including simple control, input and output.Tier 2: (Business Logic Tier)The middle tier is known as business logic process and data access.It removes performance, flexibility, maintainability, reusability and scalability.

Tier 3: (Database tier)It has data server that provides the business data.Provides data locking, consistency management and replication.

Advantage of three-tierIt is easier to modify any tier without affecting the other tier.Separating the tier leads to load balancing.Security policies enforced within the server tier.It improves the performance with large number of clients.It increases flexibility in software implementation.More scalable than two-tier architecture.

The tier is popularly used for internet applications, net-centric information system and military systems.

1) Client layer:It is also called asPresentation layerwhich contains UI part of our application. This layer is used for the design purpose where data is presented to the user or input is taken from the user. For example designing registration form which contains text box, label, button etc.2) Business layer:In this layer all business logic written like validation of data, calculations, data insertion etc. This acts as a interface between Client layer and Data Access Layer.This layer is also called the intermediary layer helps to make communication faster between client and data layer.3) Data layer:In this layer actual database is comes in the picture.Data Access Layer contains methods to connect with database and to perform insert, update, delete, get data from database based on our input data.