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A OCR Computer Science A level > Chapter 20 - Transaction processing > Flashcards

Chapter 20 - Transaction processing Flashcards

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1
Q

What are 3 examples of automated methods?

A

» Smart card readers
» Barcode readers
» Scanners

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2
Q

What are 2 examples of manual methods of data capture?

A

» Forms
» Questionnaires

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3
Q

What are 3 ways in which data can be transferred into a database?

A

» DMBS software
» Typing it into a customised form
» Using EDI

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4
Q

What does EDI stand for?

A

» Electronic Data interchange

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5
Q

What is EDI?

A

» Is the computer to computer exchange of documents such as purchase orders, invoices and shipping orders

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6
Q

What is the main requirement of using EDI, and how does it help the environment?

A

» Must be in standard format so that the computer can understand it
» It replaces post, email or fax, therefore saving paper

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7
Q

How can you select data?

A

» Using SQL

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8
Q

What is a single logical operation?

A

» Defined as a transaction

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9
Q

What is Transaction processing?

A

» Any information processing that is divided into individual, indivisible operations called transactions

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10
Q

What is the base functionality of all relational databse?

A

» Referred to using the acronym CRUD
» Create - Insert/create
» Read - Select
» Update - Update
» Delete - Delete

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11
Q

What does DBMS stand for?

A

» Database mangement systems
» Provides a layer for the user and the programmer

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12
Q

What does ACID stand for, and what is the purpose?

A

» Atomicity, Consistency, isolation, Durability
» Set of properties to ensure data integrity is maintained as well as transactions are processed reliably

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13
Q

What is Atomicity?

A

» Ensures that a transaction is processed in its entirety or not at all
» Half- completed change must not be saved back to the database

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14
Q

What is Consistency?

A

» Ensures that no transactions can violate any of the defined validation rules
» Referential integrity, will always be upheld - Meaning any change in the databse must retain the overall state of the database

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15
Q

What is isolation?

A

» Ensures that concurrent execution of transactions leads to the same result as if transactions were processed one after the other
» Transactions must not be interrupted by another transaction

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16
Q

What is durability?

A

» Ensures once a transaction has been committed, it will remain so, even in the event of system failure
» DBMS writes the effects of the transactions into secondary storage rather than RAM
» Held in buffer until all elements are compelted
» Only then will the changes to the database tables be made

17
Q

What is the purpose of record locking?

A

» Prevents simultaneous access to objects in a database in order to prevent updates being lost or inconsistencies in the data arising

18
Q

What is one problem with record locking?

A

» A dealock can arise where if 2 users are attempting to update 2 records

19
Q

What is Serialisation?

A

» Ensures that transactions do not overlap in time and therefore cannot interfere with each other or lead to updates being lost

20
Q

What are the 2 techinques of serialisation?

A

» Timestamp ordering
» Commitment ordering

21
Q

How does timestamp ordering work?

A

» If 2 transactions affect the same object, the transaction with the earlier timestamp should be applied first

22
Q

Explain how timestamp ordering works?

A

» Every object in the database has a read and write timestamp, which is updated whenever an object is read or written
» When the user tries to save an update, if the read timestamp is not the same as it was when they started the transaction, the DMBS knows another user has accessed the same object?

23
Q

What is commitment ordering?

A

» Another serialisation technique to ensure that no transactions are lost if 2 clients are simultaneously trying to update a record

24
Q

Explain how commitment ordering works?

A

» Transactions are ordered in terms of their dependencies on one another as well as the time they were initated
» Can be used to prevent deadlock by blocking one request until another is completed

25
Q

What is the purpose of inbuilt redundancy?

A

» Protects transaction data from system faliure
» Duplicate hardware is located in different geographical areas, mirrors every transaction that takes place
» If this fails, the backup system automatically takes over

26
Q

What is OCR?

A

» Optical character recognition
» Automatically reads text by interpreting the shape of the letters

27
Q

What is OMR?

A

» Optical mark recognition
» Reduces human error, mostly used in the lottery industry

28
Q

What is QBE?

A

» Query by example
» Graphical - making use of visual tables
» User doesn’t need to remember finer details

A OCR Computer Science A level (75 decks)

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