Databases. A.1

Question 1

What is data?

Answer 1

Data refers to raw data or unprocessed and hasn’t been analysed

Question 2

What is information?

Answer 2

Information is “knowledge communicated or received concerning a particular fact or circumstance.”

Question 3

What is a DBMS?

Answer 3

A DBMS is a suite of computer software providing the interface between users and a database(s).

Question 3

Difference bw Information and Data?

Answer 3

∙ Data is used as input for the computer system. Information is the output of data.
∙ Data is unprocessed facts figures. Information is processed data.
∙ Data doesn’t depend on Information. Information depends on data.
∙ Data is not specific. Information is specific
∙ Data is a single unit. A group of data which carries news is called Information.
∙ Data doesn’t carry a meaning. Information must carry a logical meaning.
∙Data is the raw material. Information is the product.

Question 4

Information System

Answer 4

Any combination of information technology and and peoples activities and the use of technology to support operations, or management.

Question 4

Database System

Answer 4

A database system is a term that is typically used to encapsulate the constructs of a data model, database Management system (DBMS) and database.

Question 5

Flat file and Database definition?

Answer 5

A flat-file database is a database stored in a file called a flat file. A flat file can be a plain text file, or a binary file.

Question 6

Data Definition

Answer 6

Defining new data structures for a database, removing data structures from the database, modifying the structure of existing data.

Question 7

Data Maintenance

Answer 7

Inserting new data into existing data structures, updating data in existing data structures, deleting data from existing data structures

Question 8

Data Retrieval

Answer 8

Querying existing data by end-users and extracting data for use by application programs

Question 9

Data Control

Answer 9

Creating and monitoring users of the database, restricting access to data in the database and monitoring the performance of databases

Question 10

Benefits of sharing data are?

Answer 10

1. Scientific integrity, 2. Increase the impact of your own research, 3. Preserve your data for future use

Question 11

Drawbacks of sharing data are?

Answer 11

1. May be personal data like financial details which shouldn’t be publicised
2. If the data contains sensitive, personal information about human subjects, it may violate the Data Protection Act, ethics codes.

Question 12

What is a transaction?

Answer 12

A transaction is a set of changes that must all be made together. Single or multiple operation as a single unit.

Question 13

Transaction state?

Answer 13

Consistent state, by ensuring that interdependent operations on the system are either all completed successfully or all canceled successfully.

Question 14

How does rollback work?

Answer 14

The transaction can be rolled back completely by specifying the transaction name in the Rollback statement or to cancel any changes to a database during current transaction.

Question 14

What is rollback?

Answer 14

The Rollback operation rolls back the transaction to the beginning of the transaction. So the database reaches to its previous state.

Question 15

What is a Transaction log?

Answer 15

Recovering a database by applying different transactions that recorded in the database log files.

Question 16

What is concurrency control?

Answer 16

In a multiuser database, the statements within multiple simultaneous transactions can update the same data. Transactions executing at the same time need to produce meaningful and consistent results.

Question 17

What is a transaction?

Answer 17

A transaction is a sequence of operations performed as a single logical unit of work. A logical unit of work must exhibit four properties, called the atomicity, consistency, isolation, and durability (ACID) properties, to qualify as a transaction.

Question 18

Atomicity?

Answer 18

A transaction must be an atomic unit of work; either all of its data modifications are performed, or none of them is performed.

Question 19

Consistency?

Answer 19

The transaction must be fully compliant with the state of the database as it was prior to the transaction. In other words, the transaction cannot break the database’s constraints.

Question 20

Isolation?

Answer 20

Transaction data must not be available to other transactions until the original transaction is committed or rolled back.

Question 21

Durability?

Answer 21

After a transaction has completed, its effects are permanently in place in the system. The modifications persist even in the event of a system failure.

Question 22

What is concurrency?

Answer 22

Data concurrency means that many users can access data at the same time.

Question 23

What are the three types of concurrency control?

Answer 23

1. Pessimistic concurrency control
2. Optimistic concurrency control
3. Last in wins

Question 24

Pessimistic Concurrency Control?

Answer 24

The data set that is being modified by one user cannot be changed by another user at the same time.