Batch processing questions and answers
Questions
Q1. Summarise the main characteristics of batch processing systems.
Q2. What does ‘offline’ mean?
Q3. What does ‘online’ mean?
Q4. State three methods of ensuring that data is entered into a system accurately.
Q5. Give a clear example that illustrates data consistency.
Q6. Describe two ways that data, which has passed all checks, may still be entered into a database incorrectly.
Q7. What is a transaction file?
Q8. Describe how a transaction file is used to update a master file.
Q9. What does multi-tasking mean?
Q10. What is a multi-user operating system?
Answers
Q1. The main characteristics of batch processing are that jobs are collected together over a period of time. Jobs are processed altogether in one go, at the same time. It is not important that the output is available immediately. Jobs are often batch processed in the middle of the night, using computers and printers when nobody else needs them. The jobs can be set up to be batch processed because it is possible to write a little program using a Job Control Language that manages the work to be done. Because the JCL manages the batch processing, once it starts, no further human intervention is required.
Q2. Offline means you are physically connected to a network but are not logged on. You therefore cannot use the resources of the network.
Q3. Online means you are physically connected to a network and are logged on. You therefore can use the resources of the network.
Q4. Batch totals, control totals and check sums help ensure that data entered into a file is accurate.
Q5. If a person’s actual age in a database is not the same as their age when calculated using their date of birth, then the data has become inconsistent. In this case, it might be because of an incorrect formula, or an incorrect date of birth or age has been entered into the system.
Q6. Data could still be entered into a database incorrectly if it is transcribed incorrectly (perhaps because the handwriting on the data capture form was hard to read), if the data was put on the form incorrectly, if there is a virus in the system that corrupts data or a if hacker has broken into the system and altered data.
Q7. A transaction file is a serial file of all of the transactions or records added in a period of time.
Q8. The transaction file is first ordered into a sequential file. The master file is then updated using this sequential file. The sequential file is cleared, ready to be used again for the next period of time. The master file is backed up in case of data loss.
Q9. Some operating systems allow you to open and run more than one application, apparently at the same time. This is called multi-tasking.
Q10. Sometimes, you need to have a database of information stored centrally but it needs to be accessed by lots of people. For example, you might have a database of products and their prices on a computer in a supermarket. Lots of terminals need to access the database. Each terminal is given a very short amount of computer time before the next terminal is serviced. This happens so quickly that each terminal thinks it is the only one with access to the database! This kind of system is known as a multi-user operating system.