Data Transparency in DBMS Quiz and Flashcards

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Questions and Answers

What does transparency refer to in a system?

Transparency refers to the separation of the higher-level semantics of a system from lower-level implementation issues.

Which type of transparency protects the user from the details of the network and even hides the existence of the network from the user?

Data Independence

Replication Transparency

Fragmentation Transparency

Network Transparency (correct)

Logical data independence refers to the immunity of user applications to changes in the physical structure of data.

False

Fragmentation refers to the division of each database relation into smaller fragments for reasons of , , and .

performance, availability, reliability Signup and view all the answers

Match the fragmentation alternatives with their descriptions:

Horizontal fragmentation = Partitioning relation into sub-relations with subset of tuples Vertical fragmentation = Defining sub-relations based on a subset of attributes Signup and view all the answers

What are the three major players responsible for providing transparency in a system?

Language/Compiler, Operating System, DDBMS Signup and view all the answers

What are the two basic alternatives for partitioning a distributed database?

Partitioned (or non-replicated) and Replicated (fully or partially) Signup and view all the answers

What factors need to be considered in distributed query processing?

All of the above Signup and view all the answers

Concurrency control ensures the synchronization of accesses to a distributed database.

True Signup and view all the answers

Distributed deadlock management includes alternatives for prevention, avoidance, and ________. (Fill in the blank)

detection/recovery Signup and view all the answers

Match the following replication protocols with their descriptions:

Eager protocol = Force updates to all replicas before transaction completion Lazy protocol = Update one copy and then propagate after transaction completes Signup and view all the answers

What are some additional issues faced in distributed databases due to the changing environment?

Looser federation, multi-database systems, growth of the Internet, peer-to-peer computing, and web growth Signup and view all the answers

What is a distributed database defined as?

A collection of multiple, logically interrelated databases distributed over a computer network. Signup and view all the answers

Which of the following are types of accesses involved in a Distributed Database System?

Local access Signup and view all the answers

What are the two main characteristics of candidate applications for a Distributed Database System?

Large number of users and users are physically spread across large geographical area. Signup and view all the answers

In a centralized Client-Server System, data management is distributed across multiple systems.

False Signup and view all the answers

In a Distributed Database System, the __________ contains the global schema.

DDBMS Signup and view all the answers

What are the three orthogonal dimensions/Alternatives of DDBS?

Delivery modes Signup and view all the answers

What is the purpose of periodic delivery in a Distributed Database System?

To send data from the server to clients at regular intervals. Signup and view all the answers

Distributed Database Systems help reduce telecommunication costs.

True Signup and view all the answers

Study Notes

Distributed Database Systems Overview

A distributed database system is a collection of multiple, logically interrelated databases distributed over a computer network.
A distributed DBMS (DDBMS) is the software system that permits the management of the distributed database and makes the distribution transparent to the users.

Characteristics of Distributed Database Systems

Data management at multiple sites: data is stored and managed at geographically multiple sites.
Local requirements: each site storing data in a DDBS is called a local site, catering to local users.
Global perspective: the DDBS fulfills global requirements in a transparent way.

Access to a Distributed Database System

Three types of accesses:
- Local access: access by users connected to a site, accessing data from the same site.
- Remote access: a user connected to a site, accessing data from another site.
- Global access: data is displayed after being collected from all locations, regardless of access location.

Application of Distributed Databases

Candidates for a DDBS have two main characteristics:
- Large number of users.
- Users are physically spread across a large geographical area.
Examples of candidates:
- Banking applications.
- Air ticketing.
- Business at multiple locations.

Data Delivery Alternatives

Three orthogonal dimensions/alternatives of DDBS exist:
- Delivery modes (pull-only, push-only, hybrid).
- Frequency (periodic, conditional, ad-hoc).
- Communication methods (unicast, multicast).

Communication Methods

Unicast: one-to-one communication from a server to a client.
Multicast: one-to-many communication from a server to multiple clients.

Distributed Database System vs Centralized Client-Server System

Centralized C/S System:
- Data management is carried out on a single centralized system.
- Data is accessed from different machines (clients) connected through a network.
- Data storage and management is mainly done on the server.

Promises of Distributed Database Systems

Four fundamental advantages:
- Transparent management of distributed and replicated data.
- Reliable access to data through distributed transactions.
- Improved performance.
- Easier system expansion.

Transparency in Distributed Database Systems

Types of transparencies:
- Data independence.
- Network transparency or distribution transparency.
- Replication transparency.
- Fragmentation transparency.
Responsibility of transparency:
- Access layer (language/compiler).
- Operating system level.
- DBMS level.

Layers of Transparency

Language/compiler provides transparency features.
Operating system provides network transparency.
DBMS provides fragmentation or replication transparency.### Distributed Database Systems (DDBS)

Critical Issues in DDBS

Consistency of data across multiple sites is a serious issue
Distributed transactions should be executed at multiple sites without fear of failure
Reliability through distributed transactions ensures user applications do not need to worry about coordinating accesses to individual local databases or site/communication link failures

Advantages of DDBS

Improved Performance

Data Localization: data is stored close to its point of use, reducing remote access delays and contention for CPU and I/O services
Query Parallelism: a query can be executed in parallel, improving performance

Easier System Expansion

Expansion can be handled by adding processing and storage power to the network
More economical than establishing a single, centralized system

Complications Introduced by Distribution

Selection of the Copy: choosing the right copy based on constraining variables (distance, load, site availability, etc.)
Failure Recovery: synchronization of copies after failure is more complex than in centralized systems
Complexity: overall system is more complex than centralized database systems
Cost: involves more cost, as hardware and trained manpower are needed at multiple sites
Distribution of Control: access to data must be carefully managed, with well-defined rights for local sites

Design Issues in DDBS

Distributed Database Design: how to place the database and applications across sites
Distributed Directory Management: global or local directories, centralized or distributed
Distributed Query Processing: deciding on a strategy for executing queries over the network
Distributed Concurrency Control: maintaining consistency of multiple copies of the database
Distributed Deadlock Management: prevention, avoidance, and detection/recovery
Reliability of Distributed DBMS: ensuring consistency and detecting/recovering from failures
Replication: fully or partially replicating the database
Relationship among Problems: design issues affect each other

Distributed Concurrency Control

Ensuring integrity of the database despite concurrent access
Two classes: pessimistic (synchronizing before execution) and optimistic (executing and checking consistency)
Two fundamental primitives: Locking and Timestamping

Distributed Deadlock Management

Alternatives: prevention, avoidance, and detection/recovery

Reliability of Distributed DBMS

Ensuring consistency of the database despite failures
Recovering from failures and bringing databases up-to-date

Replication

Ensuring consistency of replicas (copies of the same data item)
Protocols: Eager (forcing updates to all replicas before completion) or Lazy (propagating updates after completion)

Relationship among Problems

Design of distributed databases affects many areas
Directory management, query processing, concurrency control, and replication are interrelated

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Description

This quiz assesses your understanding of transparent management of distributed and replicated data, including the concept of transparency in system design. It covers how transparency enables the development of complex applications and allows users to pose queries without worrying about implementation details.

Transparent Management of Distributed Data

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