CSC 675 Review 1 - Introduction and Overview Flashcards Preview

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Flashcards in CSC 675 Review 1 - Introduction and Overview Deck (38)
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1
Q

Data

A

Known facts that can be recorded

2
Q

Database *

A

Collection of related data

3
Q

DBMS, Database Management System *

A

a collection of programs that enables users to create, access, and maintain a database

4
Q

Database Catalog / Meta-Data

A

structure of file

storage format of data items

constraints on the data

5
Q

program-data independence

A

allow the data file structure to be changed without modifying the application code

a layer in between

6
Q

What are the three major types of operations supported by database systems?

A

Create - define data

Access - query + update

Maintain - enforce integrity constrains

7
Q

Why are database applications considered to be easier to implement that traditional file based applications?

A

Because much of the functionality that you need is already defined.

8
Q

What is a database query?

A

Read and return all data which satisfy some search criteria.

9
Q

How do read-only queries differ from update queries?

A

update queries insert, delete or modify data values in the database, read-only queries don’t.

10
Q

Discuss how file based applications are different from database applications.

A

Databases are

  • self describing
  • insulation between programs and data
  • data abstraction
  • support multiple views of the data
  • sharing data and multiuser transaction processing

In traditional file systems,
- files are part of each program.

11
Q

Why is it difficult for application programers to provide integrity constraint enforcement in their application code?

A

all in one place

collecting the integrity constraints into the database makes updating the integrity constraints themselves possible without rewriting application programs.

12
Q

What is concurrency control?

A

coordinate many simultaneous transactions

13
Q

Why is concurrency control important?

A

insure that simultaneous transactions work with a consistent database and leave the database in a consistent state (consistent- > as if transactions were executed in some sequential order)

14
Q

What is recovery?

A

Insure that no data from committed transactions is lost, regardless of any failures.

15
Q

Why is recovery important?

A

All systems are prone to failures, and handling recovery from failure is a must.

16
Q

Why is redundant data a problem? *

A

The redundant data problem concerns a piece of data or data fields that is stored in one or more table locations. If the data is updated in one location is must also be updated in tall other locations, so that we know that we’re accessing the correct data. We need to ensure the integrity of the data.

17
Q

How do database systems make it easier to avoid storing redundant data? *

A

A database system makes it easier to avoid storing redundant data by keeping all the dat in one easily update able location and providing an easy mechanism to do this.

18
Q

What is a data model?

A

A collection of concepts that can be used to describe the structure of a database.

19
Q

How is a data model used?

A

Data models are the practical tools used for specifying data abstraction.

20
Q

Define the term database schema.

A

description of the database

specified during the database design

21
Q

Define the term database state.

A

The data in the database at a particular moment in time.

22
Q

Define the term data dictionary.

A

In addition to storing catalog information about schemas and constraints, the data dictionary stores other information, such as design decisions, usage standards, application program descriptions, and user information.

23
Q

Describe the main categories of data models and the differences between them.

A

High level - ER model - close to the way many users perceive data

implementation data model - Relational Model

low level - physical data models - how data is stored in the computer

24
Q

What is the difference between a database schema and a database state?

A
  • Database schema - the description of the database

- Database state - the data in the database at a particular moment in time

25
Q

What is a database view?

A

A virtual relation defined as the result of any legal SQL query. The view behaves as if it is not materialized until a query against it is executed.

26
Q

How is a database view used?

A

Views are used just like other tables. Limits the possible update operations that can be applied to views, but it does not provide any limitations on querying a view.

27
Q

Under what conditions is it NOT a good idea to use a database system for application development?

A

not likely to change

real time processing requirements

does not require concurrent data access

28
Q

Describe four types of program-data independence and give an example of each.

A

representation of numeric data: int -> float

representation of character data: fixed length string -> variable length string

units for numeric data: inches -> meters

data materialization (virtual fields): age stored directly or derived from birthdate or current date

structure of stored records: (student, sno, course, coursename_ -> (student, sno, course), (course, coursename)

structure of stored file -> ordered on sno, hashed on sno

29
Q

What are the five major components of the DB implementation architecture?

A

Scanning & Parsing

Query Optimizaion

Run-Time Environment

Transaction Manager

Access Methods

File System / OS Disk

30
Q

Explain what functions are performed by the scanning & parsing module of a DBS.

A

translate SQL request into an internal representation (and check syntax & type compatibility)

31
Q

Explain what functions are performed by the query optimization module of a DBS.

A

select “optimal” access strategy and generate query execution plan

32
Q

Explain what functions are performed by the run-time environment of a DBS.

A

interprets query execution plan, transactions

query processing

authorization & integrity checks

33
Q

Explain what functions are performed by the access methods of a DBS.

A

organize information on the disk & retrieve individual records when requested by the run-time environment

34
Q

Explain what functions are performed by the file system, OS & disk of a DBS.

A

organize disk storage

coordinate transfer of blocks of data to/from memory buffers

35
Q

What is a transaction?

A

atomic unit of database

processing (commits or aborts)!

36
Q

How does a transaction differ from an execution plan?

A

execution plan - static

transaction - executing code

37
Q

Explain what functions are performed by the transaction manager.

A

part of run- time environment

concurrency control: coordinate many simultaneous transactions

recovery: insure that no data from committed transactions is lost, regardless of any failures

38
Q

Why are the functions performed by the transaction manager important?

A

To ensure data isn’t lost.