A451 Databases

A Database is a structured set of data held in a computer, especially one that is accessible in various ways.

What is a Db?
Give example of a serial file Db
Give example of a sequential Db
Talk about 3 levels of a Db view
The external view
The conceptual view
The physical view
What is a Flat file Db?
What is a hierarchical Db?

The data in the picture could be what the database is used for and what it stores.
A database records strings of information on what to do when data is input and decides where to put it and stores it to the file showing information attached.
You gain information for the collected data.
If a phone company had to take the customers name, number, address, and email the database will record it so next time when the customer calls back you can just look through the database and find their personal file of information and you can record even more information against their file and adding notes of their bills and what they have bought as their service.
Sequence databases can be searched using a variety of methods. The most common usage is probably searching for sequences similar to a certain target protein or gene whose sequence is already known to the user. A flat file database describes any of various means to encode a database model (most commonly a table) as a single file. A hierarchical database is a management system that links records together so that each record has only one owner. It represents information in a one to many relationship, e.g. parent may have more than one child but each child can only have one parent. They were used widely in the first mainframes but can not be used often as they do not relate to the structures in the real world.

Network Topology

Star topology goes across the line and then chooses the direction to where to go to send the information
A star topology involves using a central device, such as a switch, as the connection point for all systems. The advantage of a star topology is that a break in the line affects only the system connected to that cable.

 

Bus topology slows down when heavy traffic and there is lots of data collisions.
A bus topology consists of a main cable (known as a trunk) that all systems connect to. There are terminators at each end designed to absorb the electrical signal off the network. If there were no terminators, the signal would bounce back and collide with other data on the cable. One of the disadvantages of a bus topology is that if there is a break in the trunk, the entire network fails.

 

In a ring topology, hosts are connected to each other forming a large circle. In a single-ring topology, all of the device on the network share a single cable. The disadvantages of a single-ring topology are that data only travels in one direction, and if there is a break in the ring, the entire network will go down. In a dual-ring topology, there are 2-rings made from separate cables. This allows data to be sent in both directions and introduces fault tolerance as there would need to be a break in both lines to cause the network to go down.