Principles of Data Storage

In any organisation, it is imperative that the data stored is as accurate as possible. A set of principles are implemented to ensure data accuracy.

Transaction processing

A transaction on a database comprises of a series of small actions.
For example, buying cinema tickets.
A database management system (DBMS) has to ensure that all of the possible concurrent transactions (like multiple bookings at the same time) will leave the data in the same state as if each transaction was performed one after another.

Record locking

Record locking is used to lock a record in a table until a transaction is completed.
If the transaction fails, the record is unlocked for someone else to access.

Redundancy

Databases for organisations such as hospitals, military forces and banks need to ensure they have redundancies built into their database systems.
This means they will have multiple clone database systems all running at the same time that are all mirror images of one another.

Redundancy cont.

Redundant systems are usually kept in geographically different places. These systems constantly monitor each other.
If one system goes down, then other systems can take over and will update the system that has gone down.
One of the other redundancy systems instantly takes over and continues to provide the service needed.

Atomicity, Consistency, Isolation and Durability (ACID)

ACID ensures all transactions complete successfully, or if they fail, the data is left as it was before.

Atomicity

Atomicity is the classification of transactions as a single task that either passes or fails.

Consistency

Consistency ensures that the data being committed as part of the transaction complies both with validation rules and referential integrity.
This means a record cannot be added or updated if it uses a value in a foreign key field that doesn’t exist in the linked table.

Isolation

The isolation part of the principals ensures that the data is locked whilst a transaction is processing.
The data in the database should look the same as if all transactions happened sequentially instead of concurrently.

Durability

Durability ensures that once a transaction is completed, it is committed to the database and will stay in the database for good.
When booking your cinema tickets, the DBMS will make use of a buffer and record locks to store the individual parts of a transaction until it is all completed.
At this point, the transaction is committed to the database permanently.

1Components of a Computer

1.1Structure & Function of the Processor

1.1.1Structure of the CPU

1.1.2Fetch, Decode, Execute Cycle

1.1.3Factors Affecting CPU Performance

1.1.4CPU Architecture

1.2Types of Processors

1.2.1CISC & RISC

1.2.2Multicore & Parallel Cores

1.3Input, Output & Storage

1.3.1Computer Systems

1.3.2Magnetic Storage

1.3.3Optical Storage

1.3.4Types of Optical Storage

1.3.5Types of Memory

1.3.6Flash Memory

1.3.7Virtual Memory

2Software & Software Development

3Exchanging Data

4Data Types, Data Structures & Algorithms

4.1Data Types

4.1.1Data Types

4.1.2Arrays & Strings

4.1.3Representing Numbers

4.1.4Binary Arithmetic

4.1.5Hexadecimal

4.1.6Converting Binary Numbers

4.1.7Floating Points in Binary

4.1.8Floating Point Arithmetic

4.1.9Bitwise Manipulation

4.1.10Character Sets

4.2Data Structures

4.2.1Arrays, Linked Lists & Queues

4.2.2Graphs, Hash Tables & Stacks

4.2.3Trees

4.3Boolean Algebra

4.3.1Computational Logic

4.3.2Boolean Logic

4.3.3Karnaugh Maps

4.3.4Boolean Identities

4.3.5Flip Flops & Adder Circuits

5Legal, Moral, Cultural & Ethical Issues

5.1Computing Related Legislation

5.1.1Data Protection Act (1998)

5.1.2Computer Misuse Act (1990)

5.1.3Copyright Designs and Patents Act (1988)

5.1.4Regulation of Investigatory Powers Act (2000)

5.2Moral & Ethical Issues

5.2.1Online Activity Tracking

5.2.2Censorship

5.2.3Cultural Issues

5.2.4Environmental Issues

5.2.5Layout, Colour Paradigms & Character Sets

6Elements of Computational Thinking

6.1Thinking Abstractly

6.1.1Abstraction

6.2Thinking Procedurally

6.2.1Decomposition

6.3Thinking Logically

6.3.1Pseudocode & Flow Diagrams

7Problem Solving & Programming

7.1Programming Techniques

7.1.1Programming Fundamentals

7.1.2Modularity

7.2Programming Construction

7.2.1Integrated Development Environments

7.2.2Testing

8Algorithms

8.1Algorithms

8.1.1Interpreting, Correcting & Completing Algorithm

8.1.2Sort Algorithms

8.1.3Insertion & Merge Sort

8.1.4Search Algorithms

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