What constitutes a ddb transparency Availability and Reliability Scalability & Partition Tolerance Autonomy Advantages of Distributed Database



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Distributed database

Distributed Database

A distributed database is a collection of multiple logically related database distributed over a computer network, and a distributed database management system as a software system that manages a distributed database while making the distribution transparent to the user.

Distributed Database Concepts

What constitutes a DDB

Transparency

Availability and Reliability

Scalability & Partition Tolerance

Autonomy

Advantages of Distributed Database


  1. What constitutes a DDB

Connection of database nodes over a computer network

There are multiple computers ,called nodes or sites. these sites must be connected by an underlying network to transmit data and commands among sites .

Logical interrelation of the connected databases

It is essential that the information in the various database nodes be logically related.

Possible absence of homogeneity among connected nodes

It is not necessary that all node be identical in terms of data, hardware and software.



2. Transparency

The concept of transparency extends the general idea of hiding implementation details from the end users.

A highly transparent system offers a lot of flexibility to the end users/application developer since it requires little or no awareness of underlying details on their part

Types of Transparency

1.Data Organization Transparency (Distribution/Network)

2.Replication Transparency

3.Fragmentation Transparency

4.Design Transparency

5.Execution Transparency

1. Data Organization transparency

Also known as Network or Distribution transparency

It refers to freedom for the users from the operational details of the network and the placement of data in the distributed system

Two types are

1.Location Transparency

Refers to the fact that the command used to perform a task is independent of the location of the data and the location of the node where the command was issued

2. Naming Transparency

Implies that once a name is associated with an object , the named object can be accessed unambiguously without additional specification as to where the data is located.

2.Replication Transparency

Refers to copies of the same data objects may be stored at multiple sites for better availability, performance and reliability.

This makes the user unaware of existence of these copies

3.Fragmentation Transparency

2 types of fragmentation are possible: Horizontal and Vertical Fragmentation



  • Horizontal Fragmentatiom

Distributes a relation (table) into subrelations that are subset of the tuples(rows) in the orginal relation

Also known as SHARDING in the newer big data and cloud computing systems



  • Vertical Fragmentation

Distributes a relation(table ) into subrelations that are subset of columns of the orginal relation.


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