MANUFACTURING REQUIREMENTS

Manufacturing Requirements Planning (MRP) programs help coordinate thousands of inventory items when demand for one item depends on demand for another. MRP systems determine when finished products are needed, then work backward to determine deadlines and resources needed to complete the final product on schedule.

USE OF TECHNOLOGY IN MANUFACTURING MIS

Technologies have been developed to control and streamline the manufacturing process. Computers can directly control manufacturing equipment using computer-assisted manufacturing software. Computer-integrated manufacturing software connects all aspects of production together, including order processing, product design, manufacturing, quality control, and shipping. For example, after an engineer designs a product using CAD software, MRP systems can use information from the design as input to plan and order materials. Production scheduling systems can use the design specifications as an input into the scheduling process. And computer-aided manufacturing systems can use the design specifications as input for setup. This greatly improves manufacturing efficiency.

BENEFITS OF MANUFACTURING MIS

A flexible manufacturing system allows a facility to quickly and efficiently change from making one product to making another, often using robotics and other automation. Generally the changeover is computer-controlled.

Finally, quality control has become paramount for manufacturing firms. Control charts or sample testing is used to monitor product quality.

The manufacturing MIS subsystems and outputs monitor and control the flow of materials, products, and services through the organization.

ADVANTAGES OF MIS

These are following advantages of development and management of Information technology in PEL Pakistan:

• Core competency support
• Enhance distribution channel management
• Increase brand equity
• Boost production process
• Expand E-Commerce
• Improve B2B commerce

RECOMMENDATIONS

No doubt the company is well equipped with the technology and IT professionals but even that I’d like to recommend that:

• There should be a continue review of the company polices and procedures regarding IT management to be consistent with the emerging world.
• Latest IT procedures and software must be considered for the old process as well as the new one
• IT professionals must be given periodic training to adapt the current trend in the field of IT.

CONCLUSION

Technology play a very vital role in the development and enhancement of any business so the latest and advanced technologies must be implemented and managed by highly professional to cope up with any complex situation.

MANUFACTURING MIS

Manufacturing MIS is an MIS designed specifically for use in a production environment.

OBJECTIVES OF MANUFACTURING MIS

• Material requirements planning (MRP)
• Determine when finished products are needed
• Determine deadlines accordingly
• Manufacturing resource planning (MRPII)
• Network scheduling
• Improve customer service and productivity
• Just in time (JIT) inventory system
• Inventory and materials delivered right before usage

INPUTS TO THE MANUFACTURING MIS

• Strategic plan or corporate policies.
• Order processing
• Inventory data
• Receiving and inspecting data
• Personnel data
• Production process
• External sources

MANUFACTURING MIS SUBSYSTEMS AND OUTPUTS

• Design and engineering
• Master production scheduling
• Inventory control
• Manufacturing resource planning
• Just-in-time inventory and manufacturing
• Process control
• Computer-assisted manufacturing (CAM)
• Computer-integrated manufacturing (CIM)
• Flexible manufacturing system
• Quality control and testing

INVENTORY CONTROL PROGRAM

Inventory control programs are one component of a manufacturing MIS that relies on the production schedule. Inventory control programs can forecast future production, automatically reorder items when a certain threshold is met, determine manufacturing costs, and develop resource requirements plans from the production schedule.

MIS DEVELOPMENT

The development of sound MIS is the result of the development and enforcement of a culture of system ownership. An “owner” is a system user who knows current customer and constituent needs and also has budget authority to fund new projects. Building “ownership” promotes pride in institution processes and helps ensure accountability.

MIS which meets the five elements of useability is a critical ingredient to an institution’s short- and long-range planning efforts. To achieve sound MIS, the organization’s planning process should include consideration of MIS needs at both the tactical and strategic levels. They should also be used in support of the long term strategic MIS and business planning initiatives. Without the development of an effective MIS, it is more difficult for management to measure and monitor the success of new initiatives and the progress of ongoing projects.

MIS DEVELOPMENT METHODS

Management needs to ensure that MIS systems are developed according to a Sound methodology that encompasses the following phases:

• Appropriate analysis of system alternatives, approval points as the system is developed or acquired, and task organization.
• Program development and negotiation of contracts with equipment and
• Software vendors.
• Development of user instructions, training, and testing of the system.
• Installation and maintenance of the system.

USE OF PROJECT MANAGEMENT TECHNIQUES

Management should also consider use of “project management techniques” to monitor progress as the MIS system is being developed. Internal controls must be woven into the processes and periodically reviewed by auditors. In addition, user manuals should be available and provide the following information:

• A brief description of the application or system.
• Input instructions, including collection points and times to send updated information.
• Balancing and reconciliation procedures.
• A complete listing of output reports, including samples.
• Depending on the size and complexity of its MIS system, an institution may need to use different manuals for different users such as first-level users, unit managers, and programmers.

COMPONENTS OF MIS

• Application software
• Computer hardware devices and cables

CHARACTERISTICS OF MIS

• Timeliness
• Accuracy
• Consistency
• Completeness
• Relevance

• Timeliness

To simplify prompt decision making, an institution’s MIS should be capable of

Providing and distributing current information to appropriate users. Information systems should be designed to expedite reporting of information. The system should be able to quickly collect and edit data, summarize results, and be able to adjust and correct errors promptly.

• Accuracy

A sound system of automated and manual internal controls must exist throughout all information systems processing activities. Information should receive appropriate editing, balancing, and internal control checks. A comprehensive internal and external audit program should be employed to ensure the adequacy of internal controls.

• Consistency

To be reliable, data should be processed and compiled consistently and uniformly. Variations in how data is collected and reported can distort information and trend analysis. In addition, because data collection and reporting processes will change over time, management must establish sound procedures to allow for systems changes. These procedures should be well defined and documented, clearly communicated to appropriate employees, and should include an effective monitoring system. Comptroller’s Handbook 5 Management Information Systems

• Completeness

Decision makers need complete and pertinent information in a summarized form. Reports should be designed to eliminate clutter and voluminous detail, thereby avoiding “information overload.

• Relevance

Information provided to management must be relevant. Information that is inappropriate, unnecessary, or too detailed for effective decision making has no value. MIS must be appropriate to support the management level using it.

USE OF IT TECHNOLOGY AT PEL PAKISTAN

PEL Pakistan is the largest manufacturing company of electrical equipments in Pakistan and is equipped with the latest technology to compete the global world. There are following information systems used in PEL:

• Management information system
• Finance MIS
• Manufacturing MIS
• Marketing MIS
• HR MIS
• Networking and web technologies

• Financial Management Information System

Financial MIS provides financial information regarding financial statements, uses and management of funds, and financial statistics for control to all financial managers with in the organization.

• Manufacturing MIS

Manufacturing MIS is an MIS designed specifically for use in a production environment. Manufacturing MIS is required to get:

• Designing and reengineering
• Master production scheduling
• Inventory control
• Manufacturing resource planning
• Just in time report
• Process control
• Quality control

• Marketing MIS

• Support managerial activities in :
• Product development
• Distribution
• Price decision
• And promotional effectiveness

Marketing MIS is comprise of the input of

Sales by customers, sales by sales persons, sales by product, pricing report, total service calls, and customer’s satisfaction.

• Human Resource Management MIS

This MIS is concern with all activities related to employees and potential employees of the organization.

MIS receive the input of:

• Benefit report
• Salary survey
• Scheduling reports
• Training test score
• Job application file
• Need and planning report

OBJECTIVES OF MIS

There are following objectives of MIS:

• Provide timely and needed information
• Provide support to management to achieve corporate goals
• To take quick and effective decisions.
• Identify and resolve any problem

INFORMATION TECHNOLOGY SYSTEMS IN ORGANIZATION

In the manufacturing or services businesses the role and importance of the information technology can’t be ignored because now the world become a global village where every one come and close to each other regarding multiple aspects of business and this is therefore e important to adapt and manage the up to date technologies and their management to achieve the business objectives. There are some specific aspects of technological involvement in the business as below:

• management information system
• E-business
• Intranet strategies
• Database management system
• Customer relationship management
• Enterprise resource planning (ERP)
• Business Performance Management
• Project management software
• Decision support system
• Material resource planning
• Supply chain management
• E-marketing
• E-commerce

IT MANAGERS ROLE

In any organization the implementation and management of the technologies are highly dependent upon the proficiencies and skill of IT manager therefore it is most important to have highly skilled and professional managers having following skills:

• Planning,
• Design,
• Selection,
• Implementation,
• Administration information and communications technologies

SKILL REQUIRED FOR IT MANAGEMENT

Some of the most popular information technology skills at the moment are:

• Computer Networking
• Information Security
• IT Governance
• Business Intelligence
• Project Management

ELEMENTS OF INFORMATION TECHNOLOGY

The basic components or elements of information technologies that have to be managing in an organization can be:

• Hardware
• Software
• Information systems
• Telecommunication networks

• HARDWARE

Hardware is a general term for the physical artifacts of a technology. It may also mean the physical components of a computer system, in the form of computer hardware. The hardware devices can be:

• Computers
• Server and storage
• Printers
• Scanners
• Fax

Computer

A device that computes, especially a programmable electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information

Server

A computer that makes services, as access to data files, programs, and peripheral devices, available to workstations on a network

Printers

Printer is a {peripheral} device for producing text and images on paper.

Scanners

Scanner is an electronic device that generates a digital representation of an image for data input to a computer.

Fax

A device which scans, transmits, receives and prints documents (faxes) transmitted by telephone.

• SOFTWARE

Software refers to as logical parts of computer. Computer software is a general term that describes computer programs. The programs used to direct the operation of a computer. There are two types of software:

• System software
• Application software

System Software

It helps in running the computer hardware and the computer system. System software is a collection of operating systems; devise drivers, servers, windowing systems and utilities. System software helps an application programmer in abstracting away from hardware, memory and other internal complexities of a computer.

Application Software

It enables the end users to accomplish certain specific tasks. Business software, databases and educational software are some forms of application software. Different word processors, which are dedicated for specialized tasks to be performed by the user, are other examples of application software.

• INFORMATION SYSTEMS

Information system refers to a system that provides for data collection, storage and retrieval; facilitates the transformation of data into information and the management of both data and information. An information system comprises hardware, software (DBMS and applications), the database(s), people and procedures

• TELECOMMUNICATION NETWORKS

Telecommunication networks can be defined as the transmission channels interconnecting all client and server stations as well as all supporting hardware and software. It is a high speed, high capacity, long-distance communications system comprising of computers, electronic switches, cables, satellites, wireless transmitters and antennas, etc., which link multiple remote sites.

DIFFERENCE BETWEEN IT AND IT MANAGEMENT

Management Information Systems refer to information management methods tied to the automation or support of human decision making. MIS as it is referred to is focus mainly on the business aspect with a strong input into the technology phase of the business/organization.

Whereas IT Management refers to the IT related management activities in organizations.

OBJECTIVES OF IT MANAGEMENT

These are following objectives of managing information technologies:

• Provide technology-focused services that increase productivity
• Enhance computing experiences.
• Provide a reliable, efficient, friendly and easily-accessible organization for information technology
• Deploy and support the most efficient, cost effective and reliable technologies
• Continue to support, operate and manage information technology applications, databases and communication networks in a reliable and efficient manner. Integrate new technologies and replace obsolete equipment/services to meet an ever-changing environment.
• Limit risks and any negative impacts to existing systems

SPECIFIC OBJECTIVES

• To support the organizational strategic plan and individual department business objectives through the effective use of information technology.
• To reduce the overall cost of technology through system integration
• Increase organizational productivity
• To provide advice and support in the implementation of technical solutions throughout the organization
• To automate the organization’s use of internal information to ensure that data is organized and shared in a manner that adds value and enhances productivity
  To define and support technology standards
• To maintain a reliable and secure communications infrastructure with the capacity to address future growth

INFORMATION TECHNOLOGIES

Introduction
Generally the term information technology or IT uses to refer to an entire industry. In actuality, information technology is the use of computers and software to manage information. In some companies, this is referred to as Management Information Services (or MIS) or simply as Information Services (or IS). The information technology department of a large company would be responsible for storing information, protecting information, processing the information, transmitting the information as necessary, and later retrieving information as necessary.
Definition
Information technology or IT is” The study, design, development, implementation, support or management of computer-based information systems, particularly software applications and computer hardware
Moreover IT deals with the use of electronic computers and computer software to convert, store, protect, process, transmit, and securely retrieve information.

INFORMATION TECHNOLOGY MANAGEMENT

Introduction to ITM
In recent years information technology has played a major role in our daily life by replacing human labor with automation system through hardware and software as an evaluation tool. Furthermore, we can access the world’s information just through our fingertips via Internet technology. Multimedia which requires high bandwidth several years ago can now be sent through Internet. Other technologies such as 3D and Virtual Reality are expected to be able to run on Internet in the future. As can be seen on the above mentioned examples, technology in data communication and hardware & software computer are mutually integrated and evolved rapidly in the past 5 years with continuous development expected.

Definition
Information Technology Management is concerned with exploring and understanding Information Technology as a corporate resource that determines both the strategic and operational capabilities of the firm in designing and developing products and services for maximum customer satisfaction, corporate productivity, profitability and competitiveness.

Continued from NAT-Server-3

We sniff the packets coming from the internet by simply sniffing the packets and distinguishing them from the packets from the local network packets by Checking for the destination IP address; this is because while manipulating the packets from the local network we changed the source IP to our NAT Server’s IP. So therefore all the packets coming from the Internet side would be destined for the NAT Server.

Now the Packets are re-manipulated such that the IP of the destination and the port number is now changed by first searching which of the node originated this request and then this ip address and the port number is changed accordingly.

Sending packets back in the network

Now when all the basic NAT process is done we send the packet back in the network where it reaches the respective node.

IMPORTANT FUNCTIONS

Some of the main functions which contribute to the proper working and implementation of our NAT Server are as follows:

Get_start_list():

This function along with the callback () function is used for sniffing the packets and extracting the fields of headers of different layers. This is the main combination of function which contributes a major portion to the sniffing process.

Update record:

This function is used to maintain the database for the nodes for which we have sent the data on the internet.

Time_to_live:

This function is used in synchronization with the reply of the packets sent on the internet

Search_db:

This function searches the maintained database when a reply from the internet comes, for determining which node in the internal network originated this request.

Make_tcp:

This function is used for the manipulating the packet which is to be NAT.

Make_udp:

This is used for the manipulation of the UDP packet to send on the internet.

IMPORTANT TECHNIQUES

Some of the important techniques used while implementing the NAT server are that we have done the sniffing technique using the socket programming library. Different processes of time to live, sniffing and database update and synchronized using posix threads using the pthread.h library.

Choices And Assumptions

First of all: we have to take make a change in approach of using two network interface card for local and outside network, this is because we are modeling the NATing Technique and not implementing the firewall in our design. In short we are only implementing the SNAT.

Secondly: we this design is implemented with consideration that we have a small network of about two or three nodes because of the memory limitation of the machines in the lab and at our home of handling large traffics.

Thirdly: COMPLEXITY IN IMPLEMENTATION

While implementing the NAT Server the first difficulty which we faced was of sniffing the packet and correctly extracting the fields of the headers of different layers this problem was solved by thoroughly studying the related topics by taking help from the google.com and by using function such as ntohs(), e.g. to read total length field of the IP header. Second complexity which was raised was of correct Checksum of the packet at different layers this obstacle was cleared by carefully calculating the parameters of the checksum function. Thirdly and mainly we are having some problems with the reply back of the packets sent on the internet and as the reply are so un-predictable that nothing can be said about it.

Conclusion

In the end we have tried our best to meet the design of the SNAT to provide internet access to the local network connect to the NAT Server but there are still some complexities which are hindering the server to completely function as a true NAT Server.

Continue from NAT-Server-2

NAT Server operate on IP packet-level, most of them have built-in inter-network routing capability. The inter-network they are serving can be divided into several separate sub networks (either using different backbones or sharing the same backbone) which further simplify network administration and allow more computers to be connected to the network:

NAT works at Layer 3 of OSI

In Short a NAT Server provides the following facilities:

Automatic firewall protection for the internal network; only destination request originated from the internal network will be accessible from the Internet

Automatic client computer configuration control

Packet level filtering and routing

Phases of Implementation

The implementation of Nat Server consists of the following phases:

Building a Sniffer

Manipulating the sniffed packets

Maintaining a record of the synchronized nodes and their packets

Sending the manipulated packets on the internet

Sniffing the incoming packets from the internet

Sending those packets back in the local network

Building a Sniffer

First of all we make a sniffer which can sniff the packets which collide with our network interface card. For this purpose we have to make the respective function which is able to receive the packet and store them for further manipulation. By further manipulation we mean that validating the sniffed packets and extracting the information stored in all the respective headers encapsulated along with data.

After we have sniffed the packets correctly we have to extract the header information from the packets. First of all the Ethernet header is inspected.

Ethernet Header:

The Ethernet header consists most importantly the MAC addresses of both the source and the destination hosts. We extract this information from here.

IP Header:

Next comes the IP header this has the ip addresses of both source and destination, the protocol which defines the protocol was used on the upper layer. We extract all the information stored in this header.

TCP/UDP/ICMP header:

In the upper layer one of these three protocols are used which is defined in the protocol field of the IP header. We also extract the information from this header, which completes our sniffing part.

Manipulating the sniffed packets

After the sniffing is complete we know alter the packets received as required for the NAT process. This is done by changing the IP address of the source and the by assigning a new port number to the packet which is now to be sent on the internet, for this purpose we make another packet having all the same values as the original packet except the source IP and the port no which is assigned according to our maintained database for the outgoing packets.

Maintaining a record

Once our packet is ready to be sent to the internet we make a table like database of the nodes for which we have manipulated the packets for and distinguish their different requests from the new port numbers assigned to them by our manipulating function.

Sending Packets on the Internet

After all the process of sniffing and maintaining databases we know send the packets on the internet through the pcap.h library functions of sending the packet.

Sniffing the internet packets

Continue from NAT-Server-1

Each client has a time-out associated with it. Whenever new traffic is received for a client, its time-out is reset. When the time-out expires, the client is removed from the table. This ensures that the table is kept to a reasonable size. Also most of NAT implementations also track TCP clients on a per-connection basis and remove them from the table as soon as the connection is closed. This is not possible for UDP traffic since it is not connection based.

As the port mapping table has complete connection information – source and destination address as well as the port numbers – it is possible to check any of this information before passing incoming packets back to the client. This checking helps to provide effective firewall protection against Internet-launched attacks on the private LAN.

Each IP packet also contains checksums that are calculated by the originator. They are recalculated and compared by the recipient to see if the packet has been corrupted in transition process. The checksums depend on the contents of the packet. Since the NAT must modify the packet addresses and port numbers, it must also recalculate and replace the checksums.

IMPORTANCE of NAT

IP Address Consideration

An IP address is 4 bytes, the total number of available addresses is 2 to the power of 32 = 4,294,967,296. is the total theoretical number of addresses that can be allocated to the computers that can be directly connected to the Internet. While this number of available addresses seems large, however if we connect each computer with the internet by assigning a unique address every node then this number is in-sufficient. While the next generation IP protocol, IP version 6, allows for larger addresses, it will take years before the existing network infrastructure migrates to the new protocol.

Because of this major problem shortage of IP addresses, most Internet Service Providers only allocate one address to a single customer, and most of the time this address is assigned dynamically, so every time a client connects to the ISP a different address will be provided. With an NAT gateway running on this single computer, it is possible to share that single address between multiple local computers and connect them all at the same time. The outside world is unaware of this multiplexed environment and takes the network as a signal computer.

Security Considerations

Another issue is of the security of the network or any other personal computer. To tackle the security problem, a number of firewall products are available. They are placed between the user and the Internet and verify all traffic before allowing it to pass through. This means, for example, that no unauthorized user would be allowed to access the computer’s resources. The problem with firewall solutions is that they are expensive and difficult to set up and maintain, putting them out of reach for home and small business users. NAT automatically provides a firewall protection without any special set up. This is because it only allows connections that are requested from local network. This means, for example, that an internal client can connect to an outside FTP server, but an outside client will not be able to connect to an internal FTP server.

Administrative Considerations

NAT is helpful to a network administration in several ways:

It can divide a large network into several smaller ones. The smaller parts expose only one IP address to the outside, which means that computers can be added or removed, or their addresses changed, without impacting external networks. With inbound mapping, it is even possible to move services (such as Web servers) to a different computer without having to do any changes on external clients.

Some of the modern NAT Servers contain a dynamic host configuration protocol (DHCP) server. DHCP allows client computers to be configured automatically; when a computer is switched on, it searches for a DHCP server and obtains TCP/IP setup information. Changes to network configuration are done centrally at the server and affect all the clients; the administrator does not need to apply the change to every computer in the network. The new configuration will be assigned to the node next time it starts.

This project report provides the implementation of NAT-Network Address Translate Server. It gives the detailed description of different phases of implementation of NAT Server. NAT Server hosting allows us to share a common internet connection between multiple computers on a network. The project implementation under discussion is done in Microsoft Visual C++. The machine running the NAT Server has network connection through one network card (or modem) and allows computers connected to a network visible through the second server network card to share its internet connection. The project is completed and function with the TCP, UDP and ICMP internet protocols.

The basic purpose of a NAT Server is to multiplex traffic from the network and present it to the outer world (Internet) as if it was coming from a single computer having only one IP address.

The TCP/IP protocols include a multiplexing facility so that any computer can maintain multiple simultaneous connections with a remote computer. It is this multiplexing facility that is the key to single address NAT.

To multiplex several connections to a single destination, client computers label all packets with unique “port numbers”. Each IP packet starts with a header containing the source and destination addresses and port numbers.

The TCP/IP connection is completely defined by a combination of these IP and port numbers. The addresses specify the two machines at both ends, and the two port numbers ensure that each connection between this pair of machines can be uniquely identified.

Each unique source port number in the client can originate a separate connection, and all reply packets to these requests contain the same number as their destination port, so that the client can maintain record as to which the application originated the respective request. In this way it is possible for a web browser on the client to ask a web server for several frames at once and to know how to put all the parts of all the responses back together.

A NAT Server must change the Source address on every outgoing packet to be its single public address. It therefore also renumbers the Source Ports to be unique, so that it can keep track of each client connection. The NAT Server uses a port mapping table to remember how it renumbered the ports for each client’s outgoing packets. The port mapping table relates the client’s real local IP address and source port plus its translated source port number to a destination address and port. By using this technique it can reverse the process for returning packets and route them back to the respective clients.

When any remote server responds to an NAT client, incoming packets arriving at the NAT gateway will all have the same Destination address, but the destination Port number will be the unique Source Port number that was assigned by the NAT. The NAT Server looks in its port mapping table to determine which of its own local client address and port number a packet is destined for, and replaces these numbers before passing the packet on to the client.

When a packet is received from an internal client, NAT looks for the matching source address and port in the port mapping table. If the entry is not found, a new one is created, and a new mapping port allocated to the client:

Incoming packet received from local client

Look for source address, port in the mapping table

If found, replace source port with previously allocated mapping port

If not found, allocate a new mapping port

Replace source address with NAT address, source port with mapping port

Packets received from the outside world undergo a reverse translation process:

Incoming packet received from Internet

Look up destination port number in port mapping table

If found, replace destination address and port with entries from the mapping table

If not found, the packet is not for us and should be rejected

Prominently, Oracle is the name of the database management system that is introduced by the Oracle Corporation.

Referring to Oracle products, Oracle9i is the latest product released by Oracle Corporation. In comparison to Oracle products and unlike Oracle8i, which is only a database management system, Oracle9i comprises of the following software:

Oracle9i Application Server – Oracle9iAS

Oracle9i Database Server – Oracle9iDB

Oracle9i Developer Suite – Oracle9iDS

More elaborately, Oracle9i is a platform and not a simple database management system.

By the way, Oracle9iDB is the database management system that is used to store and access data. Oracle is the most widely used relational database management system (RDBMS).

Be acknowledged, the Oracle Corporation is second largest software company next to Microsoft. Oracle Corporation has been targeting Internet programming with the caption – software powers the internet.

Furthermore, Oracle Corporation is also into Enterprise Resource Planning (ERP). It has Oracle Applications that includes Oracle Financials and many more.

The Oracle Database-Server

As we know that Oracle database server is one of the databases that are widely used in client/server computing as back-end. Front-end programs that are written using application development tools such as Visual basic access Oracle and submit SQL commands for execution.

Oracle8i onwards oracle is trying to provide extra facilities that are required to be an internet database.

We know that the Oracle8i provides special features to support various types of data that is to be stored in web sites. Oracle supports both OLTP (online transaction processing) applications as well data warehouse applications, which contain a very large database (VLDB).

One of the biggest advantages of Oracle has been its presence on around 100 different platforms. Oracle is quite scalable, which means it can scale up and down very easily as the requirements change.

Oracle also provides Java Virtual Machine (JVM) as part of database. This enables oracle to run java programs. In fact, starting from Oracle8i, oracle can run programs written either in PL/SQL or Java.

What is Oracle Instance?

The Oracle instance is a collection of memory structures and processed that is used to manage oracle database. Each oracle database is to be accessed by one or more Oracle instances. If two or more instances are accessing the same database, it is called as parallel server architecture.

Whenever we start using an oracle database, we must first start Oracle instance. Oracle instance will them open the database and make it available to users.

Furthermore in the nutshell, every oracle installation contains at least one Oracle Instance and one oracle database

Understanding a Personal-Oracle

When talking about the Personal Oracle, it is one of the flavors of Oracle. This is not a product that is used by production system (systems where real data is stored). Elaborately, this is more like a learning tool since it runs on desktop PCs. In personal oracle, oracle instance, oracle database and client application all run on the same machine (see figure 3). Unlike others, in the Oracle database server, only oracle instance and database reside on the server and client applications run on clients.

Moreover, it is also possible to develop an applications using Personal Oracle on your desktop/laptop and deploy them in a client/server environment.

OSI PHYSICAL LAYER

Topology: Physical arrangements of the network.

Transmission Media: The type of media we will use to send information.

Types of Topology:

Bus Topology:

Advantages: It’s the cheapest type of topology, easy to implement, used on smaller networks and can be used in distributed networks.

Disadvantages: It’s a passive technology in which a user cannot regenerate signals. Number of users is limited and if its break on any one point whole network will be dead.

Ring Topology:

Advantages: it’s an active topology because it can regenerate signals. Easy to implement and can be used in distributed networks

Disadvantages: It was also need at a certain extent because it was not available to all the users what we want. If it is break on any one point whole network will be dead.

Star Topology:

Advantages: There is a central connecting device by which every computer is connected separately. If one physical link is break only this computer will be dead, it will not disturb the others. It can be passive as well as active topology. It was passive before now it is active due to LAN Switches which checks, examines and regenerates the signal. It can support large number of users.

Disadvantages: Expensive as compared to other topologies.

Central Device: Ethernet – Hub, Ethernet – Switch, Token Ring – MAU.

Star – Bus Topology / Hybrid:

When it’s a combination of star and bus such as star is within the building and to connect buildings we use bus topology.

WAN Topologies:

In WAN (World Wide Area Network) we have four topologies.

Daisy Chain: When computers at different cities are connected to each other like a bus topology. The head of one is connected to the tail of another. It’s not purely like a bus, the network are connected to one another in form of links. If one link of networks is dead the other will be disconnected, it’s slow. It is used only where branch office is connected to head office and secondly the importance of time and response is not needed.

Hub & Spoke: When networks are connected to one another in the form of star topology, there is one central network which is connected to all other network. If one link is down, the others will not be disturbed. It’s faster than the daisy chain but its cost is higher than the previous one. Cost is dependent on the distance and geographical location.

Mesh Topology: Any source has more than one links exist is called mesh topology. Its selected due to when the time of link is critical in mesh a single point is connected to every other point. It’s very reliable as compared to other types. We need more links to connect these points, if one link is down that other links will not be interrupted.

Partial Mesh Topology: Every link is not connected to every another link but still using more than one path to transmit information to link. Its combination of daisy chain with fully mesh or hub & spoke. It’s not necessary you use a single topology in WAN, you combine different topologies depending on the business scenario by taking care of pros and cons.