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Batch Processing

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Introduction

Batch Processing Using batch processing input data is grouped together into batches. No data is processed until a complete batch has been put together. Then all the data in a batch is processed in one go. There may be a long time delay between data being input into the system and the data being processed. In this type of system the important data that the computer stores all the time is kept in a file called the master file. The data in the master file is sorted into order using one of the fields in the records in the file, known as the primary key field. The primary key field must uniquely identify each record in the file. Each piece of input data (which will update the contents of the master file) is known as a transaction. All the input data is put together into a batch in a file called the transaction file. There are three different types of transaction that any processing system will have to cope with. They are: * Add a new record to the master file. * Delete a record from the master file. * Amend / update an existing record in the master file. At some predetermined time (e.g. the end of the day or week) the computer system will process the data stored in the transaction file and make any changes that are necessary to the master file as a result of the transactions. This will produce an updated master file and an error report detailing any transactions that could not be processed for some reason. ...read more.

Middle

At the end of the week the transaction file would be processed. Before processing it would have to be sorted into the same order as the master file, i.e. records in order of employee number. The computer would then process the transactions, using the information about how many hours each employee has worked this week (from the transaction file) and their rates of pay (from the master file) to calculate the employee's wages for the week. Payslips can then be printed and the master file can be updated to increase the amount paid so far this year by the wages paid this week. An error report will also be produced. Transaction Processing (or Interactive or On-Line or Pseudo Real Time Processing) For some applications the master file needs to be kept up to date all of the time. For example in a travel agents whenever a seat is booked on a flight the number of seats that remain available on the flight must be reduced by one immediately. If this update was not done until the end of a day (as might happen in a batch processing system) then the flight could become overbooked. Transaction processing systems are used whenever the master file must be kept up to date. A transaction processing system operates like this: When a transaction is entered it is placed in a queue of transactions waiting to be made. The transactions are processed in the order that they are placed into the queue. ...read more.

Conclusion

There is a real world time limit on how long the computer system can take to process data without having terrible consequences. Therefore a missile control system has to be a real time system. Most real time systems are control systems. Other examples include the cooling system in a nuclear reactor, which prevents the reactor overheating, or any system, which must control a dangerous chemical reaction. Real time systems are very fast but they do not process data instantly. Any processing will take some time. However real time systems will process data very quickly. To ensure that any input data can be processed sufficiently quickly real time systems must incorporate a lot of redundancy. This means having much more hardware than is required to process the expected amount of input data. The extra hardware is known as redundant hardware because it is not normally used. Under normal circumstances only a small fraction of the hardware is required. In extreme circumstances when there is an unusually large amount of input data to process the redundant hardware can be used. Therefore the system will not slow down and will still be capable of meeting deadlines. Having to incorporate lots of redundant hardware makes real time systems very expensive. They are usually only used in safety critical situations. Advantage of Real-time Systems Disadvantage of Real-time Systems If real-time systems were not available we would not be able to do certain jobs. E.g. missile guidance. Real-time systems are very expensive to produce and require lots of development time and backup hardware (redundancy). EMMA MOORE - 1 - ...read more.

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