ADBMS - unit 3 & 4: intro to DDBMS & Arch

Question 1

What is distributed database system?

Answer 1

A distributed database is a database that runs and stores data across multiple computers, as opposed to doing everything on a single machine.

Question 2

What is Node or Instance?

Answer 2

Typically, distributed database systems operate on two or more interconnected servers on a computer network. Each location where a version of the database is running is often called an instance or a node.

Question 3

How instance runs on centralized and on distributed?

Answer 3

A distributed database, for example, might have instances running in New York, Ohio, and California. Or it might have instances running on three separate machines in New York. A traditional single-instance database, in contrast, only runs in a single location on a single machine.

Question 4

what is distributed in D dbms

Answer 4

1. program logic
2. functions
3. data
4. control

Question 5

synonymous terms for D DBMS

Answer 5

distributed data processing

multiprocessors / multi computers

satellite processing

backend processing

dedicated / special purpose computers

timeshared systems

functionally modular systems

peer to peer systems

Question 6

What is DDB system

Answer 6

• DDB is collection of multiple, logically interrelated databases distributes over a computer network

Question 7

what is D DBM system software

Answer 7

D-DBMS is the s/w that manages the DDB and provides an access mechanism that makes this distribution transparent to the users

D DBMS = DB + communication

Question 9

Why not D DBMS

Answer 9

timesharing computer system
loosely or tightly coupled multiprocessor system
database system which resides at one of the nodes of a network of computers - this is a centralized database on a network node

Question 10

distributed dbms promises

Answer 10

transparent management of distributed, fragmented, and replicated data

improved reliability / availability through distributed transactions

improved performance

easier and more economical system expansion

Question 11

what is meaning of “Promises of Distributed Databases”

Answer 11

Promises of distributed databases, meaning advantages of distributed databases

Question 12

what is first promise of distributed database

Answer 12

First promise or advantage of distributed database is
1. transparency of data, fragmentation and replication

Question 14

what is transparency transparency

Question 15

Explain transparency of data, fragmentation and replication

Answer 15

• transparency refers to separation of the higher level semantics of a system from lower level implementation issues
• DDBMS hides all the added complexities of distribute allowing users to think that they all working with a single centralized systems

eg:
engineering firm that has offices in boston, mumbai, paris, and delhi

• they run projects and maintain database of these employees ex: projects, employees etc
• let us assume that the database is relational and stored in following two relations

Emp( eno, ename, title )
Proj( Pno, Pname, Budget )

• the other relation to store salary information

SAL(Title, Amt)

the 4 relation to know the assign projects with duration and responsibility indicates as

ASG( eno, pno, resp, dur )

if we want to find out the names and employees who worked on a project for more than 12 months the query that we all going to write is:

select ename amt
from ASG.dur > 12
AND Emp.eno = ASG.eno
AND sal.title = emp.title

based on queries it is going to search in different databases of boston paris etc…

in order to quick processing of query we are going to partition each of the relations and store each partition at a different siet
this is known as fragmentation

2. data independence DI
   - DI is a fundamental form of transparency
   - it is capacity of changing the database scheme at one level of database system without efficiency the schema at the next higher level

2 types
- logical DI
- physical DI

LDI stores information about how data is managed inside

PDI deals with hiding the details of the storage structure from user applications

if network transparency / distribution transparency

• other than data the user should be protected from the operational details of the network
• allowing a user to access a resource (application program or data) without the user needing to know whether the resource is located on the local machine or on a remote machine

3. replication transparency

• replication transparency ensures that replication of databases are hidden from the users
• it enables users to query upon a table as if only a single copy of the table exists

4. fragmentation transparency

• dividing each database relation into smaller fragments and treat each fragment as a separate database object
• this is for reasons of performance, availability and reliability

so to provide easy and efficient access of the DBMS we need to have fully transparency

Question 16

what is second advantage of promise of distributed database

Answer 16

reliability through distributed transactions

Question 17

explain reliability through distributed transactions

Answer 17

• distributed DBMSs are designed to improve reliability by having replicated components results in eliminating failures
• so the failure creates problem to the entire system
• in distributed proper case is taken such that instead of failure part user may be permitted to access other parts of the distributed database
• this is useful to support for distributed transactions
• a transaction is a basic unit of consistent and reliable computing, consisting of a sequence of database operations executed as an atomic action

ex: transaction based on the engineering firm
- assuming that there is an application that updates the salaries of all the employees by 10%

• in the middle of this transaction if system fails we would like the DBMS to be able to determine, pon recovery, where it left off and continues with its operation
• distributed transactions execute at a no. of sited at which they access the local database
• here we are providing a facility that there is no interruption in any transaction

-

Question 18

what is third promise or advantage of distributed databases

Answer 18

improved performance

• a distributed DBMS fragments the conceptual database, this is also called as data localization

advantages
1. since each site handles only a portion of the database, correction for CPU and I/O services is not severe

• localization reduce remote access delays
• implementation of inherent parallelism of distributed system
• it has enter query and infra query parallelism
• inter query parallelism - to execute multiple queries at the same time
• intra query parallelism is achieved by breaking up a single query into a number of sub queries each of which is executed at a different site, accessing a different part of the distributed database

Question 19

what is fourth advantage or promise of distributed database

Answer 19

4. easier system expansion

in a distributed environment it is mush easier to accommodate increasing database sizes

in general expansion can be handled by adding processing and storage power to the network

• this also depends on the overhead of distribution
• one aspect of easier system expansion is economics
• it normally costs much less to put together a system of smaller computers with equivalent power of a single big machine

Question 20

what are some problem areas

Answer 20

complexity

data replication

overall cost

security issue

integrity control

lacking standards

Question 21

explain complex nature of D DBMS

Answer 21

distributed databases, are network of many computers present at dif. location and they provide an outstanding level of performance, availability and of course reliability

therefore nature of distributed database is more complex than centralized database

we also need complex and advance software’s to manage distributed databases

also it ensures no data replication, which adds even more complexity in its nature

Question 22

explain overall cost in detail

Answer 22

costs such as maintenance cost, procurement cost, hardware cost, network / communication costs, labor costs etc, adds up to the overall cost and make it costlier than normal DBMS

Question 23

explain security issues of distributed databases

Answer 23

• along with maintaining no data redundancy/duplication, security of data as well as a network is a prime concern
• network can be easily attacked for data theft and misuse

Question 24

Explain integrity control

Answer 24

• in vast distributed database system, maintaining data consistency is important
• all changes made to data at one site must be reflected on all the sites
• the communication and processing cost is high in distributed DBMS in order to enforce the integrity of data

Question 25

what is standardization

Answer 25

the process of transforming data from various sources into a consistent format, ensuring uniformity in data structure, naming conventions, and values, allowing for easier integration, organization

Question 26

abstract view ka kya matlab hota he

Answer 26

abstract view ka matlab hota he, jis tarike se database kam kar raha he, usse upar upar se samjana

internally uske andar nahi jhakte jyada

upar upar se dekhte he ki kya kya components lage hue he

konse konse components aapas me communicate kar rahe he

ye sari chize ham study karte he

Question 27

architectural model kya hote he? ye hame kya show karte he

Answer 27

arch models hame abstract view of distributed systems show karte he

Question 28

arch models se kya help hoti he

Answer 28

arch models system ki reasoning ko simplify karne me help karte he

Question 29

architectural models for distributed DBMS

Answer 29

client-server
peer to peer
multi database

Question 30

Client servers explain.
1. What it is consists of
2. what are responsibilities of servers
3. How clients and servers are connected

Answer 30

1. clients and servers
2. hosting, managing and delivering services to clients
3. clients and servers are connected through computer network, and they communicate over internet

Question 31

Client - server arch
1. How does it work

Answer 31

1. when client need services, it sends request to server, server processes request sends response to client

Question 32

explain step by step how client interacts with server

Answer 32

1. user enter URL in browser
2. browser sends request to DNS server to lookup the IP address of the web server
3. DNS sends IP address of the web server to browser
4. browser sends http/ request to IP address of srever
5. web server sends necessary files back to browser
6. browser render files and display data

Question 33

client server model me konse konse process hote he

Answer 33

clienst server model me hamare pas do types ke process hote he

1. client process
2. server process

Question 34

hamare pas jo do processes he, client process and server process

usme se konsi process requesting process he

Answer 34

jo do processes he, client process and server process, usme se client process ko requesting process kaha jata he

Question 35

jo do chize hamare pas hoti he client server architecture me, clients and servers usme se kise “service providing” kaha jata he

Answer 35

hamare pas jo do processes he, client and server usme se client ko requesting service kaha jata he

aaur server ko, providing service kaha jata he

Question 36

client server konse protocol par kam karta he

Answer 36

client server request/reply protocol par kam karta he

Question 38

what are types of C-S arch

Answer 38

1. two tier
2. three tier
3. N tier

Question 39

advantages of client server

Question 40

disadvantages of client server

Question 41

use cases of client server

Answer 41

FTPs
Web servers
web browsers
DNS