Class Notes, Database

Component of A Database System(DBS)

My flight was late, so I missed the first day of class(intro), and I doubt there is anything in the first day of class.

This is the second day of my class.

Database system is a system that centered around data, comprising of 5 parts :

1.Hardware.

   This is where the data is stored at. Information ages advances as the cause of data. We find more ways to store data. All information is stored into hardware’s component like zip drive, floopy disk, CD/DVD and the like, hard drives, etc. Even this wordpress blog data is stored somewhere on WordPress’s server that is a raid of hard drive. Looking downwardly, information is just bits, which has 0 or 1 possibility, ON or OFF, Written or Not Written. So a word document that is 11KB for example is a stream of  90112 bits(11*1024*8), is stored in a hard drive.

   Data not only needs to be stored but it also needs to be retrieved and accessed as fast as possible. Data storage nowadays come with CPU also, which helps in calculating the queue of processing time.

2.Software / Applications.

   Many of us did not realize that we use Software application everyday to connect to the Database. We usually go to the web browser like firefox, opera, google chrome, etc to get to the internet to retrieve whatever information we needs, but that information must be stored somewhere? Yes. On the website owner’s database, either his own computer or the computers provided by web hosting companies.

   Say, for example, after you type in cnn.com onto your web brower’s address bar, you usually see that boring phrase on the lower left corner : “Watiting for cnn.com…..” and after that “Connecting to cnn.com” and then boom you see the main page. Well, the whole process is complicated but it can be simplified as this. As you connecting to cnn.com, actually, your web browser sent packet of information to the Domain Name System (DNS) to find the host name cnn.com and waiting for response. This DNS can be thought of as a DBS since it stored every host name. The DNS would then connect the browser to cnn.com by sending back acknowledgement messages.More clearly, some websites have you have premium account to access their data like ACM,etc.

3. Data (the most important part).

   Yeah! The most important part that is the less written. It is what it is-data or stream of bits.

   Data is organized mostly in three ways :

   a. sequential.

   b. random access.

   c. relational.

4. People.

– Customer ‘ s value.

– Administrator.

5.Procedure : control user’s activity.

Well ? It will be easier if you look at the big picture :

Database big picture

Database Management System:

Well, this is the layer that sits on top of the Database that do a lot of complicated things.

Formal Definition : A set of programs used to define, process, and administer the Database and its applications.

Functions:

a. Store, retrieve and update user data.

b. Store, retrieve, and update data dictionary (records/fields format).

c. Enforce integrity rule so contraints data [data shacking]. ==> make sure data input is the right format.  [GIGO = Garbages In Garbage Out]

d. Enforce security constraints.

e. Provide and coordinate control frailities for multi-user processing.

f. Provide methods for backup and recovery.

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