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1.6 Database - transaction processing (Automated Methods (smart card…
1.6
Database - transaction processing
Manual Methods of Data Capture
Data from forms that are filled out by hand often need to be typed in manually
Automated Methods
smart card readers
barcode readers
scanners
optical character recognition (OCR)
optical mark recognition (OMR)
magnetic ink character recognition
sensors
Inputting Data
Once data has been collected, it can be transferred to a database
•automatically, using the DBMS software
•by typing it in using a customised form
•importing it from a spreadsheet or file
•using EDI (Electronic Data Interchange) – this is used to transfer data between one computer system and another
Electronic Data interchange (EDI)
Electronic Data interchange (EDI) is the computer-to-computer exchange of documents such as purchase orders,
invoices and shipping documents between two companies or business partners
It replaces post, email or fax
All documents must be in a standard format so that the computer can understand them
EDI translation software may be used to translate the EDI format
so the data can be input directly to a company database
Selecting Data
Using SQL or, for example, Query By Example in Access, data satisfying specific criteria can be selected and ordered
It can then be used in reports, letters, mailing labels, to print out barcodes, etc.
Transaction Processing
In the context of databases, a single logical operation is defined as a transaction
It may consist of several operations; for example, a customer order may consist of several order lines…
•all of which must be processed…
•the quantity of each product adjusted on the stock file…
•credit card details checked…
•payment accepted or rejected
ACID (Atomicity, Consistency, Isolation,
Durability)
ACID stands for Atomicity, Conswistency, Isolation, Durability
This is a set of properties to ensure that the integrity of the database is maintained under all circumstances
It guarantees that transactions are processed reliably
Atomicity
- This property requires that a transaction is processed in its entirety or not at all
In any situation, including power cuts or hard disk crashes, it is not possible to process only part of a transaction
Consistency
- This property ensures that no transaction can violate any of the defined validation rules
Isolation
- This property ensures that no transaction can violate any of the defined validation rules
Durability
- This ensures that once a transaction has been committed, it will remain so, even in the event of a power cut
As each part of a transaction is completed, it is held in a buffer on disk until all elements of the transaction are completed
Only then will the changes to the database tables be made
Mulit-User Database
Allowing multiple users to simultaneously access a database could potentially cause one of the updates to be lost
