Some of the advantages of DDBMS over centralized DBMS are: Reflects organizational structure Improved share ability and local autonomy Improved availability Improved reliability Improved performance Economics 1. Reflects organizational structure We can distribute the data base over any organization offices which has distributed locations For example: A bank has many branches in different areas. It […]

Distributed Database Management System Distributed Database Management System (DDBMS) is a type of DBMS which manages a number of databases hoisted at diversified locations and interconnected through a computer network. It provides mechanisms so that the distribution remains oblivious to the users, who perceive the database as a single database. Features of distributed database management […]

Definition of Multimedia A combination of different ways of conveying information such as using texts, sounds, videos ,images, animations and interactivity. Definition of Distributed Multimedia Systems Distributed multimedia systems consist of multimedia databases, proxy and information server , and clients, and are intended to for the distribution of multimedia content over the networks. Architecture of […]

Definition of Distributed System A distributed system is a network that consists of autonomous computers that are connected using a distribution middleware. They help in sharing different resources and capabilities to provide users with a single and integrated coherent network. Examples of Distributed Systems 1. Intranets A single authority protected access – a firewall. Services: […]

Some of the characteristics of multimedia data are: Continuous Time based Compression Bulky Needed special hardware’s 1. Continuous Multimedia data means video and audio data as continuous and time dependent.Multimedia data refers to the continuous data stream.Here, continuous refers to the user’s view of data. Multimedia data are represented as sequences of discrete values that […]

Introduction to distributed scheduling Scheduling refers to the execution of non-interactive processes or tasks at designated times and places around a network of computer. Distributed scheduling refers to the chaining of different jobs into a coordinated workflow that spans several computers. For example: – you schedule a processing job on computer1 and computer2, and when […]

Deadlock Deadlock is a fundamental problem in distributed systems. A process may request resources in any order, which may not be known a priori and a process can request resource while holding others. If the sequence of the allocations of resources to the processes is not controlled. A deadlock is a state where a set […]

Task Migration It is the movement of an executing task from one host processor in distributed computing system to another. Task placement is the selection of a host for a new task and the creation of the task on that host. Benefits of task Migration Load Balancing: Improve performance for a distributed computing system overall […]

Introduction A distributed scheduler is a resource management component of a distributed operating system that focuses on judiciously and transparently redistributing the load of the system among the individual units to enhance overall performance. Users submit tasks at their host computers for processing. Why load distribution algorithm needed ? The need for load distribution arises […]

Various middleware languages like RMI required to make successful communication between distributed objects. Stub and skeleton objects works as communication objects in distributed system. RMI means remote method invocation. Whenever needed RMI invokes the methods at client and server side objects. As shown in above diagram, in RMI communication follows the following steps: A stub […]

External data representation At language-level data are stored in data structures At TCP/UDP-level data are communicated as ‘messages’ or streams of bytes – hence, conversion/flattening is needed Converted to a sequence of bytes Problem? Different machines have different primitive data reps, Integers: big-endian and little-endian order float-type: representation differs between architectures char codes: ASCII, Unicode […]

Client server communication Clients and servers exchange messages in a request response messaging pattern. The client sends a request, and the server returns a response. This exchange of messages is an example of inter-process communication. To communicate, the computers must have a common language, and they must follow rules so that both the client and […]

Election Algorithm Many distributed algorithm require one process to acts as coordinator, initiator, or otherwise perform some special role. The goal of an election algorithm is to ensure that when an election starts concludes with all process agreeing on who the new coordinator is to be. Types of Election Algorithm Token ring algorithm Bully Algorithm […]

Definition of DSM A distributed shared memory is a mechanism allowing end-users’ processes to access shared data without using inter-process communications. In other words, the goal of a DSM system is to make inter-process communications transparent to end-users. Message passing vs. DSM Message passing Distributed shared memory Variables have to be marshaled Variables are shared […]

Two main purposes of using files: Permanent storage of information on a secondary storage media. Sharing of information between applications. A file system is a subsystem of the operating system that performs file management activities such as organization, storing, retrieval, naming, sharing, and protection of files. A good distributed file system provides the following types […]

It is architecture that offers a clear separation of the main concern and provide access to the file by using file services . Three basic components 1. Flat file service It is concern with implementing operation of the file for the service unique file identifiers are used unique file identifiers are the long sequence of […]

File Application A distributed file application consists of one or more local or remote clients that communicate with one or more servers on several machines linked through a network. With this type of application, business operations can be conducted from any geographical location. For example, a corporation may distribute the following types of operations across […]

Distributed Shared Memory(DSM) Architecture What ? The distributed shared memory (DSM) implements the shared memory model in distributed systems, which have no physical shared memory The shared memory model provides a virtual address space shared between all nodes The overcome the high cost of communication in distributed systems, DSM systems move data to the location […]

STRUCTURE OF SHARE MEMORY SPACE Structure defines the abstract view of the shared memory space. The structure and granularity of a DSM system are closely related three approaches: ·         No structuring ·         Structuring by data type ·         Structuring as a database  1. NO SRTUCTURING:- Ø  The shared memory space is simply a linear array of words. ADVANTAGE:- Ø  Choose any […]

Designing and implementation issues in DSM system 1. Granularity When a nonlocal memory word is referenced, a chuck of memory containing the word is fetched from its current location and put on the machine making the reference. An imported design issue is how big should the chuck be? A word, block, page or segment(multiple page). […]

Issues in designing distributed system 1. Heterogeneity The Internet enables users to access services and run applications over a heterogeneous collection of computers and networks .Internet consists of many different sorts of network their differences are masked by the fact that all of the computers attached to them use the Internet protocols to communicate with […]

HARDWARE AND SOFTWARE CONCEPTS Hardware concepts :- Hardware in Distributed Systems can be organized in several different ways: Shared Memory (Multiprocessors , which have a single address space). Private Memory (Multicomputers, each CPU has a direct connection to its local memory). Multiprocessors – Bus Based Have limited scalability Cache Memory help avoid bus overloading. Multiprocessors […]

Goals of Distributed Systems The four important goals that should be met for an efficient distributed system are as follows: 1. Connecting Users and Resources The main goal of a distributed system is to make it easy for users to access remote resources and to share them with others in a controlled way. It is […]

A distributed system is a model in which components located on networked computers communicate and coordinate their actions by passing messages to each other. Categories of distributed computing system models Minicomputer model Workstation model Workstation – server model Processor – pool model Hybrid model 1. Minicomputer Model The minicomputer model is a simple extension of […]

Distributed System A collection of autonomous computers linked by a network using software to produce an integrated computing facility. There are different advantages and disadvantages of distributed system they are as follows: Advantages 1. Performance: Distributed systems allow for greater overall service performance than systems whose function is centralized in a single location. By spreading […]