MANIPULATION AND/OR PROCESSING Modes of Processing Main modes of processing! Batch Processing Pseudo real time processing Real time TRANSACTIONS Transactions are events that need to be recorded in connection with the production, sale, and distribution of goods and services. Everytime you withdraw cash from a cash machine, you are performing a transaction that has to be recorded and at some point in time used to update the balance in your account. Some banks do this late at night when all customers balance are updated (batch processing). Other banks update the balance straight away (pseudo real time processing).
Others transaction e. gs include: Buying an item in a store Taking out a library book Applying for a driving license Master files and transaction files A master file is a collection of records holding information about an entity such as a person or good. It is data that will not change very often maybe once/twice a year. E. g employee name address etc A transaction file holds info about an event occurring in an organization. These will be altered more often maybe weekly BATCH PROCESSING Batch processing = a no. of documents collected over a period of time and then processed together in one.
Typiccaly in to batches of 50 documents. Adata control clerk has the responsibility of: Counting the documents Checking each one visually to see that the customer has entered the essentials Calculating a control total of crucial fields e. g Total payable for entire batch of 50 documents. Calculate hash total for fields such as size/quantity Filling in a batch header document which will show batch number, no. of documents in batch, date received, control total, hash toal Logging a total in a book kept for this purpose. INTERACTIVE PROCESSING.
Interactive Processing, data is entered and processed straight away. Organisations such as insurance companies use this. Some interactive systems allow queries to be made, but cannot process transactions straight away e. g Cash point machines which will allow you to query your balance and withdraw cash but will not update the balance until late at night. Point of sale terminals which can access stock files to look up the description and price of an article (use a bar code) but does not alter the quantity in stock when a sale is made. (This is done later in batch) REAL TIME + PSEUDO REAL TIME PROCESSING.
Real Time processing occurs when a comp responds automatically to events occurring e. g. computer control of an aeroplane. In data processing of a more mundane nature e. g. selling tomatoes in safeway , a system where the computer records a transaction and more or less straight away the master file is termed pseudo real time because of the few seconds delay in oppose to real time which is instantaneous. e. g. of pseudo time is British airways booking system which is operated by a central computer at heathrow, linked to thousands of BA agents in the UK. CRITERIA FOR CHOOSING PROCESSING MODE:
The choice of using batch or pseudo time depends on: Whether the info obtained from the system needs to be completely up to date at all times The Scale Of The Operation. Batch processing is suited to large volumes of data of the same type, When it becomes economical to have an off line key to disk system. COST A real time system is generally more expensive due to the more complex backup and recovery procedures. * Computer Usage Advantage of a batch system is that it can make use of spare comp capacity overnight or at times when the comp would be idle. Batch processing is often carried out on mainframe computers.
Many applications use a combination of batch and interactive processing! DISSEMINATION + DISTRIBUTION Dissemination of Information Characteristics of good information Computers are capable of generating unimaginable amounts of data. To make the info useful, which could be used to make a decision in business for example, info needs to be: Relevant Complete Accurate Clear Timely Info must be available when needed Concise principle of reporting by exception is very important I management info systems in other words only items that need action on them are reported In appropriate sequence.
Presenting Management Information The way info is presented can be almost as important as the info itself. The info can be presented in numerous ways: * On a comp printout * On VDU. It could be taken form a report or a slide show produced using a presentation graphics package. * Desktop published, incorporating company logo, graphs, diagrams, photographs * Using videoconferencing to enable several people at separate locations to participate meetings and exchange info. ver a company wide internet an internal network which all employees have access to and on which important information can be posted.
The Intended Audience The way that info is presented will depend to an extent on who it is intended to reach. The audience. Graphs and Charts Graphs and charts are an effective way of presenting information and highlighting problems and trends. A bar chart can be used to show trends at a glance a line graph ____________________________________________ totals but, it has no effect if there are to many. Guidelines for presentations A presentation can be a talk accompanied by an overhead projector transparencies or slide, or a slide show prepared on powerpoint. Either way, the information on each screen or slide should be:
Simple no more than 5 or 6 clearly legible lines, in clear English Brief bullet points are a good communication tool Visually appealing dont use to many different fonts, or all uppercase letters. Graphs and charts are useful where numeric information has to be imported. HARDWARE NATURE, CAPABILITIES AND LIMITATIONS Storage Devices A high intensity floppy disk has storage of 1. 44(Mb) it has a write protect hole built in. A Zip disc has a storage capacity of 100-250Mb A hard disk for a PC has a capacity typically between 500mb 5Gigabytes Magnetic Tape is a serial medium i.e. an individual record can only be accessed by starting at the beginning and every record read until the required one is found.
Magnetic tape is cheap and convenient for backup and archiving past transactions. CD Rom can store 680Mb equivalent to 100 floppy disks. Not writable, can contain multimedia WORM Write once read many times or CRW a writable CR OUTPUT DEVICES Printers Printers come in all shapes and sizes, the type of printer chosen for a job depends on these factors: Volume of data Quality of print required Location of printer Requirement for multiple copies.
Requirement of colour Different types of printer are: * Dot matrix very cheap, slow, noisy and poor quality * Ink jet reasonable price, colour cheap, medium speed and sound * Laser more expensive,very good quality, expensive colur, faster and quieter SECURITY AND DATA PRIVACY the recognition that certain data only for authorized personnel e. g doctors. SECURITY application of safeguards to protect from accidental or malicious destruction of data. Under the data protection act every organization that stores data about members of the public/employees has a duty to keep data secure i. e.secure from prying, falling into wrtong hands, accidental loss/damage. Potential threats to an info system.
Physical environment in which processing takes place needs to be safe e. g from fire, floods System design failure failure to build system into the design the appropriate measures. Hardware Processor failures, system crash, hardare stolen Communication Gateway down, Data corruption, cable faults and data could be intercepted Software bugs, unsuitable to tasks, tamper free, robust, cannot be copied by operators * Document documents could be destroyed or damaged disgruntled employee (accidental/deliberate).
Personnel DP operatives could give away passwords or be subject to personnel threats. DISASTER PLANNING Cost of lack of planning for computer failure can ruin an organization. The main consequence of computer failure is loss of business, other problems include loss of credibility, cashflow interruptions, poorer service to customers and loss of production. Many companies have comprehensive backup strategies, Even after suffering severe bomb/fire damage can be up and running in a few days. PREVENTING DATA BEING DESTROYED/CHANGED * Discs not allowed onto a system or they must be checked for viruses before use.
User Ids and passwords allowing only authorized users * Access rights different levels of access for different users, This coulb be read only, Read/Write, No access. These can be applied to files, fields and/or records BACKUP STRATEGIES Simplest backup strategy for a small business is to copy hard disc contents dailyto a DAT tape or removable disc. However if it is only necessary to copy software programs when they are changed, so a better solution is to keep data files in a separate directories from the software and selectively backup only certain directories.
If this still results in huge quantities of data , It can be reduced by backing up only those files which have changed since the last back up- an incremental backup. Backup devices come with special software that helps you to select which files to copy, when and how. KEEPING BACKUP SAFE Backup copies should be ion fire proof safes preferably off site. How long should you keep backups? Daily backups for a week Weekly for a month Monthly for a year To prevent mix up give each copy a serial number and keep a logbook.
BACKUP HARDWARE For small quantities of data, removable discs are simplest e.g. Zip drives 100Mb Super disk drives take 120Mb and can read ordinary 1. 44Mb disk. For larger backups magnetic tape is preffered e. g. Hewlett Packard cost 2Gb tape cartridges. Rewritable optical disk takes about 650 Mb RAID (Redundant Array Of Inexpensive Discs) BACKING UP ONLINE DATABASES When a database is online and being constantly updated, precautions have to be taken to ensure the data is not lost in the event of hardware falure e. g. disk head crash. Methods include: Transaction Logging info about every transaction is recorded on a separate transaction file.
A before image and an after image of any record being updated is saved so that it is part of the database is destroyed by a disk failure , an up to date copy can be created from the backup copy togeather with the transaction log using a utility program. Using RAID These devices use a technology that enables data to be hand written simultaneously to several discs. 3 copies of the database may be held, two in the same room and 1 at a remote location, and all 3 copies are kept completely up to date. Then if 1 fails the data is still safe in the other 2. FACTORS IN A BACKUP STRATEGY.
Frequency of backups Backup Medium Location of backup storage Number of generations to be kept Reponsibility of implementing the backup strategy Testing of recovery procedures NETWORK ENVIRONMENTS LAN and WAN A LAN is a local area network. It is connected by a physical cable A WAN is a Wide Are Network. It is connected by some form of telecommunications A WAN is a wide geographical structure with more than one site A LAN is restricted to a single building/room Advantages of LANs It allows the sharing of resources such as disc storage, Printers, Scanners.
Allows sharing of info held on disc drives accessible to all users easier to store applications so one computer and make them available to all users.Alows electronic mail to be sent between users It is easier to set new users and equipment Allows the connection of different types of computer which can communicate with each other. Disadvantages of LANs User dependant on them e. g. file server develops a fault then many users will be unable to run applications programs If the network stops operating then it may not be possible to access various hardware and software resources.
The efficiency of the network is very dependant on the skill of the system manager It is difficult to make the system secure e. g. Hacker As traffic increases on the network the performance degrades unless it is properly designed. Requirements of A Network Any sort of networks require maintenance someone has to be responsible for ensuring that Response time is adequate Hardware is upgraded when necessary The required software is loaded.