Data capture

Manual methods

Data from forms that are filled out by hand are then typed in to a computer manually

Automated methods

these are methods that automatically input data into a data base

• smart card reader

• barcode reader

• scanners

• optical character recognition

• optical mark recognition

• magnetic ink character recognition

• sensors

Inputting data

Once data has been collected it can be transferred to a data base. Then once the data is analysed, any meaning found is known as information.

EDI - Electronic Data interchange

The EDI is the computer-to-computer exchange of documents. This is the digital replacement for business post, email and fax, because it is used by many businesses all the documents should be kept in a standard format to prevent errors.

EDI translation

this software is used to translate an EDI format document into raw data that a company can use in their data base

Transaction processing

In the context of a databases a transaction is a single logical operation. One transaction can be made up of several steps.

ACID

ACID stands for Atomicity, Consistency, Isolation, Durability

ACID is used to ensure that the integrity of the database is maintained under any circumstances.

Atomicity

This ensures that if any part of the transaction fails it is cancelled. This is to ensure integrity of transactions and protect the money of a customer.

Consistency

This is to ensure that no transaction can violate any of the defined validation rules. This ensures that any foreign relationships are preserved.

Isolation

This ensures concurrent transactions lead to the same result as if the transactions are processed one after the other

Durability

This is to ensure that if a power cut occurs after the transaction is completed the transaction remains complete. This is achieved by having each part of a transaction stored on a buffer disk until all the elements are completed then it will make changes to the main database

Multi user databases

This allows many users to simultaneously access and change data in a database.

• When an item is to be updated, the entire block is read into the user’s local memory

• When the record is saved the block is rewritten to the file server

Record locking

record locking prevents simultaneous access to the same record. This is to prevent changes made while the record is on a local device from being overwritten when the record is then saved. It does this by stopping access to the record when it is on a local system.

Dead locks

If two users are attempting to update two records, a dead lock can happen when both records are inaccessible to each other as they both want to alter the other one. e.g.

• Ken is attempting to make a transfer from Customer A’s account to Customer B’s account

• Meanwhile, Paula is attempting to make a transfer from Customer B’s account to Customer A’s account

Serialisation

this is implemented by the database management system to prevent such situations from arising. It does this through serialisation.

Time stamp ordering

every object in the data base has a read timestamp and a write timestamp. These will updated whenever an object is read or written. This prevents dead lock if the read timestamp is not the same as this means there has been another access in the time that a user has had the record. It will reject the mismatching read timestamps.

Commitment ordering

this is another serialisation technique. It does this by ordering transactions in terms of their dependencies on one another as well as the time they were initiated. This prevents dead lock by blocking one request until another is completed

Redundancy

Many organisations have built-in redundancy in their computer systems. It will duplicate hardware, located in different geographical areas, mirrors every transaction that happens on the main database.