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Understanding Distributed Databases by Chris Ward, Coding Serbia 2015
Understanding Distributed Databases by Chris Ward, Coding Serbia 2015
Published: 2015/10/26
Channel: Coding Serbia Conference
DBMS - Distributed Database System
DBMS - Distributed Database System
Published: 2018/01/30
Channel: Tutorials Point (India) Pvt. Ltd.
Build Your Own Distributed Database With Go
Build Your Own Distributed Database With Go
Published: 2018/05/08
Channel: Coding Tech
Introduction to Distributed Database in Hindi  | DDB tutorials #1
Introduction to Distributed Database in Hindi | DDB tutorials #1
Published: 2018/04/18
Channel: Last moment tuitions
"The hows and whys of a distributed SQL database" by Alex Robinson
"The hows and whys of a distributed SQL database" by Alex Robinson
Published: 2017/09/30
Channel: Strange Loop
Distributed Database Introduction | Features | Advantages and Disadvantages
Distributed Database Introduction | Features | Advantages and Disadvantages
Published: 2017/05/16
Channel: Easy Engineering Classes
Distributed Databases
Distributed Databases
Published: 2014/01/12
Channel: Harifa Ahmed
System Design : Distributed Database System Key Value Store
System Design : Distributed Database System Key Value Store
Published: 2018/07/07
Channel: Tushar Roy - Coding Made Simple
Centralised vs Distributed Databases
Centralised vs Distributed Databases
Published: 2016/07/19
Channel: Christopher Kalodikis
Architectures in Distributed database in Hindi | Distributed database tutorials
Architectures in Distributed database in Hindi | Distributed database tutorials
Published: 2018/05/06
Channel: Last moment tuitions
Competency 6.2 Distributed Database Management Systems ITSE 2309
Competency 6.2 Distributed Database Management Systems ITSE 2309
Published: 2013/10/09
Channel: David Trevino
Distributed Database Systems (CS)
Distributed Database Systems (CS)
Published: 2016/09/23
Channel: Vidya-mitra
Vertical fragmentation in Hindi | Distributed Database Tutorials
Vertical fragmentation in Hindi | Distributed Database Tutorials
Published: 2018/05/06
Channel: Last moment tuitions
Distributed Databases - Transparency, Replication, Horizontal and Vertical Fragmentation, Allocation
Distributed Databases - Transparency, Replication, Horizontal and Vertical Fragmentation, Allocation
Published: 2012/09/11
Channel: StudyYaar.com
Google I/O 2013 - Distributed Databases Panel: An Exploration of Approaches and Best Practices
Google I/O 2013 - Distributed Databases Panel: An Exploration of Approaches and Best Practices
Published: 2013/05/20
Channel: Google Developers
Horizontal fragmentation in Hindi | Distributed Database Tutorials
Horizontal fragmentation in Hindi | Distributed Database Tutorials
Published: 2018/05/06
Channel: Last moment tuitions
What is DISTRIBUTED DATABASE? What does DISTRIBUTED DATABASE mean? DISTRIBUTED DATABASE meaning
What is DISTRIBUTED DATABASE? What does DISTRIBUTED DATABASE mean? DISTRIBUTED DATABASE meaning
Published: 2016/11/09
Channel: The Audiopedia
Distributed Databases 01
Distributed Databases 01
Published: 2015/07/17
Channel: Amritha Iyer
Wilson Hsieh - Spanner: Google
Wilson Hsieh - Spanner: Google's Globally-Distributed Database - OSDI 2012
Published: 2015/05/10
Channel: Kurt Schwehr
Trent McConaghy  - BigchainDB : a Scalable Blockchain Database, in Python
Trent McConaghy - BigchainDB : a Scalable Blockchain Database, in Python
Published: 2016/05/31
Channel: PyData
Derived horizontal fragmentation in Hindi | Distributed Database Tutorials
Derived horizontal fragmentation in Hindi | Distributed Database Tutorials
Published: 2018/05/06
Channel: Last moment tuitions
Distributed Database
Distributed Database
Published: 2017/03/26
Channel: Devin Shannon
Lessons learned from building a globally distributed database service... - Dharma Shukla (Microsoft)
Lessons learned from building a globally distributed database service... - Dharma Shukla (Microsoft)
Published: 2017/07/03
Channel: O'Reilly
Blockchain vs Traditional Databases. Is Blockchain the Future? (the Investigation)
Blockchain vs Traditional Databases. Is Blockchain the Future? (the Investigation)
Published: 2018/03/15
Channel: Crypto Coins
Design Issues in Distributed database  Hindi | Distributed database tutorials
Design Issues in Distributed database Hindi | Distributed database tutorials
Published: 2018/05/06
Channel: Last moment tuitions
What is a Distributed Database | Distributed Database Examples | Dbms Interview Questions
What is a Distributed Database | Distributed Database Examples | Dbms Interview Questions
Published: 2016/10/15
Channel: Wikitechy Interview Tips
Types of Distributed Database | Data Storage (Fragmentation, Replication) | Transparency
Types of Distributed Database | Data Storage (Fragmentation, Replication) | Transparency
Published: 2017/05/16
Channel: Easy Engineering Classes
DBMS - Features of Distributed Database System
DBMS - Features of Distributed Database System
Published: 2018/01/30
Channel: Tutorials Point (India) Pvt. Ltd.
Phases of Distributed Query Processing in DDB | Distributed Database Tutorials
Phases of Distributed Query Processing in DDB | Distributed Database Tutorials
Published: 2018/05/09
Channel: Last moment tuitions
Build your own distributed database - GopherConSG 2018
Build your own distributed database - GopherConSG 2018
Published: 2018/05/05
Channel: Singapore Gophers
Two phase commit protocol in DDB | Distributed Database Tutorials
Two phase commit protocol in DDB | Distributed Database Tutorials
Published: 2018/05/09
Channel: Last moment tuitions
Distributed DBMS Architecture
Distributed DBMS Architecture
Published: 2018/03/07
Channel: Rajesh Pathak
DBMS   Query Processing in Distributed Database
DBMS Query Processing in Distributed Database
Published: 2018/03/25
Channel: Tutorialspoint - Simply Easy Learning
Distributed Query Processing | Simple Join, Semi Join Processing | Parallelism
Distributed Query Processing | Simple Join, Semi Join Processing | Parallelism
Published: 2017/05/16
Channel: Easy Engineering Classes
Fragmentation and correctness rules in Hindi | Distributed Database Tutorials
Fragmentation and correctness rules in Hindi | Distributed Database Tutorials
Published: 2018/05/06
Channel: Last moment tuitions
Distributed Database Architecture
Distributed Database Architecture
Published: 2018/03/15
Channel: Jaquen H'Ghar
Apache Cassandra Tutorial | Understanding That Cassandra Is A Distributed Database
Apache Cassandra Tutorial | Understanding That Cassandra Is A Distributed Database
Published: 2015/01/20
Channel: O'Reilly - Video Training
DBMS   Advantages of Distributed Database System
DBMS Advantages of Distributed Database System
Published: 2018/03/25
Channel: Tutorialspoint - Simply Easy Learning
Concurrency Control Protocol in Distributed Database in Hindi |DDB tutorials in Hindi
Concurrency Control Protocol in Distributed Database in Hindi |DDB tutorials in Hindi
Published: 2018/05/08
Channel: Last moment tuitions
New Era in Distributed Computing with Blockchains and Databases
New Era in Distributed Computing with Blockchains and Databases
Published: 2017/07/04
Channel: IEEE Computer Society Silicon Valley
Distributed Database Architecture (COM)
Distributed Database Architecture (COM)
Published: 2017/02/02
Channel: Vidya-mitra
Getting Started with Apache® Ignite™ as a Distributed Database
Getting Started with Apache® Ignite™ as a Distributed Database
Published: 2018/02/15
Channel: GridGain Systems
Horizontal vertical and Mixed fragmentation of Distributed database
Horizontal vertical and Mixed fragmentation of Distributed database
Published: 2018/06/14
Channel: Dharmpal Singh
Three phase commit protocol in DDB | Distributed Database Tutorials
Three phase commit protocol in DDB | Distributed Database Tutorials
Published: 2018/05/09
Channel: Last moment tuitions
INTRODUCTION TO FRAGMENTATION AND HORIZONTAL FRAGMENTATION
INTRODUCTION TO FRAGMENTATION AND HORIZONTAL FRAGMENTATION
Published: 2017/12/26
Channel: Gold Green
Query optimization technique in distributed database system
Query optimization technique in distributed database system
Published: 2014/12/12
Channel: Satish Chavan
Distributed Database Management system
Distributed Database Management system
Published: 2016/10/22
Channel: Sibongakonke Shange
Exercises on distributed database
Exercises on distributed database
Published: 2017/05/13
Channel: محمد الدسوقى
Oracle - Create Database Link
Oracle - Create Database Link
Published: 2014/03/08
Channel: Lê Ngọc
IT344 - Chapter 25 - Distributed database - By Hala Ayash
IT344 - Chapter 25 - Distributed database - By Hala Ayash
Published: 2015/09/14
Channel: Omnia A
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WIKIPEDIA ARTICLE

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A distributed database is a database in which storage devices not all are attached to a common processor.[1] It may be stored in multiple computers, located in the same physical location; or may be dispersed over a network of interconnected computers. Unlike parallel systems, in which the processors are tightly coupled and constitute a single database system, a distributed database system consists of loosely coupled sites that share no physical components.

System administrators can distribute collections of data (e.g. in a database) across multiple physical locations. A distributed database can reside on organized network servers or decentralized independent computers on the Internet, on corporate intranets or extranets, or on other organization networks. Because distributed databases store data across multiple computers, distributed databases may improve performance at end-user worksites by allowing transactions to be processed on many machines, instead of being limited to one.[2]

Two processes ensure that the distributed databases remain up-to-date and current: replication and duplication.

  1. Replication involves using specialized software that looks for changes in the distributive database. Once the changes have been identified, the replication process makes all the databases look the same. The replication process can be complex and time-consuming depending on the size and number of the distributed databases. This process can also require a lot of time and computer resources.
  2. Duplication, on the other hand, has less complexity. It basically identifies one database as a master and then duplicates that database. The duplication process is normally done at a set time after hours. This is to ensure that each distributed location has the same data. In the duplication process, users may change only the master database. This ensures that local data will not be overwritten.

Both replication and duplication can keep the data current in all distributive locations.[2]

Besides distributed database replication and fragmentation, there are many other distributed database design technologies. For example, local autonomy, synchronous and asynchronous distributed database technologies. These technologies' implementations can and do depend on the needs of the business and the sensitivity/confidentiality of the data stored in the database, and the price the business is willing to spend on ensuring data security, consistency and integrity.

When discussing access to distributed databases, Microsoft favors the term distributed query, which it defines in protocol-specific manner as "[a]ny SELECT, INSERT, UPDATE, or DELETE statement that references tables and rowsets from one or more external OLE DB data sources".[3] Oracle provides a more language-centric view in which distributed queries and distributed transactions form part of distributed SQL.[4]

Today the distributed DBMS market is evolving dramatically, with new, innovative entrants and incumbents supporting the growing use of unstructured data and NoSQL DBMS engines, as well as XML databases and NewSQL databases. These databases are increasingly supporting distributed database architecture that provides high availability and fault tolerance through replication and scale out ability. Some examples are Aerospike,[5] Cassandra,[6] ArangoDB,[7] Clusterpoint,[8] ClustrixDB,[9] Couchbase,[10] Druid (open-source data store),[11] FoundationDB,[12] NuoDB,[13] Riak[14], MongoDB and OrientDB.[15] The blockchain technology popularised by bitcoin is an implementation of a distributed database.[16]

Architecture[edit]

A database user accesses the distributed database through:

Local applications
applications which do not require data from other sites.
Global applications
applications which do require data from other sites.

A homogeneous distributed database has identical software and hardware running all databases instances, and may appear through a single interface as if it were a single database. A heterogeneous distributed database may have different hardware, operating systems, database management systems, and even data models for different databases.

Homogeneous Distributed Databases Management System[edit]

In homogeneous distributed database, all sites have identical software and are aware of each other and agree to cooperate in processing user requests. Each site surrenders part of its autonomy in terms of right to change schema or software. A homogeneous DBMS appears to the user as a single system. The homogeneous system is much easier to design and manage. The following conditions must be satisfied for homogeneous database:

  • The data structures used at each location must be same or compatible.
  • The database application (or DBMS) used at each location must be same or compatible.

Heterogeneous DDBMS[edit]

In a heterogeneous distributed database, different sites may use different schema and software. Difference in schema is a major problem for query processing and transaction processing. Sites may not be aware of each other and may provide only limited facilities for cooperation in transaction processing. In heterogeneous systems, different nodes may have different hardware & software and data structures at various nodes or locations are also incompatible. Different computers and operating systems, database applications or data models may be used at each of the locations. For example, one location may have the latest relational database management technology, while another location may store data using conventional files or old version of database management system. Similarly, one location may have the Windows operating system, while another may have UNIX. Heterogeneous systems are usually used when individual sites use their own hardware and software. On heterogeneous system, translations are required to allow communication between different sites (or DBMS). In this system, the users must be able to make requests in a database language at their local sites. Usually the SQL database language is used for this purpose. If the hardware is different, then the translation is straightforward, in which computer codes and word-length is changed. The heterogeneous system is often not technically or economically feasible. In this system, a user at one location may be able to read but not update the data at another location.

Important considerations[edit]

Care with a distributed database must be taken to ensure the following:

  • The distribution is transparent — users must be able to interact with the system as if it were one logical system. This applies to the system's performance, and methods of access among other things.
  • Transactions are transparent — each transaction must maintain database integrity across multiple databases. Transactions must also be divided into sub-transactions, each sub-transaction affecting one database system.

There are two principal approaches to store a relation r in a distributed database system:

A) Replication
B) Fragmentation/Partitioning

A) Replication: In replication, the system maintains several identical replicas of the same relation r in different sites.

  • Data is more available in this scheme.
  • Parallelism is increased when read request is served.
  • Increases overhead on update operations as each site containing the replica needed to be updated in order to maintain consistency.
  • Multi-datacenter replication provides geographical diversity, like in Clusterpoint[17] or Riak.[18]

B) Fragmentation: The relation r is fragmented into several relations r1, r2, r3....rn in such a way that the actual relation could be reconstructed from the fragments and then the fragments are scattered to different locations. There are basically two schemes of fragmentation:

  • Horizontal fragmentation - splits the relation by assigning each tuple of r to one or more fragments.
  • Vertical fragmentation - splits the relation by decomposing the schema R of relation r.

A distributed database can be run by independent or even competing parties as, for example, in bitcoin or Hasq.

Advantages[edit]

  • Management of distributed data with different levels of transparency like network transparency, fragmentation transparency, replication transparency, etc.
  • Increase reliability and availability
  • Easier expansion
  • Reflects organizational structure — database fragments potentially stored within the departments they relate to
  • Local autonomy or site autonomy — a department can control the data about them (as they are the ones familiar with it)
  • Protection of valuable data — if there were ever a catastrophic event such as a fire, all of the data would not be in one place, but distributed in multiple locations
  • Improved performance — data is located near the site of greatest demand, and the database systems themselves are parallelized, allowing load on the databases to be balanced among servers. (A high load on one module of the database won't affect other modules of the database in a distributed database)
  • Economics — it may cost less to create a network of smaller computers with the power of a single large computer
  • Modularity — systems can be modified, added and removed from the distributed database without affecting other modules (systems)
  • Reliable transactions - due to replication of the database
  • Hardware, operating-system, network, fragmentation, DBMS, replication and location independence
  • Continuous operation, even if some nodes go offline (depending on design)
  • Distributed query processing can improve performance
  • Single-site failure does not affect performance of system.
  • For those systems that support full distributed transactions, operations enjoy the ACID properties:
    • A-atomicity, the transaction takes place as a whole or not at all
    • C-consistency, maps one consistent DB state to another
    • I-isolation, each transaction sees a consistent DB
    • D-durability, the results of a transaction must survive system failures

The Merge Replication Method is popularly used to consolidate the data between databases.[19]

Disadvantages[edit]

  • Complexity — DBAs may have to do extra work to ensure that the distributed nature of the system is transparent. Extra work must also be done to maintain multiple disparate systems, instead of one big one. Extra database design work must also be done to account for the disconnected nature of the database — for example, joins become prohibitively expensive when performed across multiple systems.
  • Economics — increased complexity and a more extensive infrastructure means extra labour costs
  • Security — remote database fragments must be secured, and they are not centralized so the remote sites must be secured as well. The infrastructure must also be secured (for example, by encrypting the network links between remote sites).
  • Difficult to maintain integrity — but in a distributed database, enforcing integrity over a network may require too much of the network's resources to be feasible
  • Inexperience — distributed databases are difficult to work with, and in such a young field there is not much readily available experience in "proper" practice
  • Lack of standards — there are no tools or methodologies yet to help users convert a centralized DBMS into a distributed DBMS[citation needed]
  • Database design more complex — In addition to traditional database design challenges, the design of a distributed database has to consider fragmentation of data, allocation of fragments to specific sites and data replication
  • Additional software is required
  • Operating system should support distributed environment
  • Concurrency control poses a major issue. It can be solved by locking and timestamping.
  • Distributed access to data
  • Analysis of distributed data

See also[edit]

References[edit]

  1. ^ "Definition: distributed database". www.its.bldrdoc.gov. 
  2. ^ a b O'Brien, J. & Marakas, G.M.(2008) Management Information Systems (pp. 185-189). New York, NY: McGraw-Hill Irwin
  3. ^ "TechNet Glossary". Microsoft. Retrieved 2013-07-16. distributed query[:] Any SELECT, INSERT, UPDATE, or DELETE statement that references tables and rowsets from one or more external OLE DB data sources. 
  4. ^ Ashdown, Lance; Kyte, Tom (September 2011). "Oracle Database Concepts, 11g Release 2 (11.2)". Oracle Corporation. Archived from the original on 2013-07-15. Retrieved 2013-07-17. Distributed SQL synchronously accesses and updates data distributed among multiple databases. [...] Distributed SQL includes distributed queries and distributed transactions. 
  5. ^ "Aerospike distributed database". Aerospike. 
  6. ^ "Apache Cassandra database menagement system". Apache.org. 
  7. ^ "ArangoDB Cluster Architecture". ArangoDB.com. 
  8. ^ "Clusterpoint XML distributed database". Clusterpoint. 
  9. ^ "Frequently Asked Questions about ClustrixDB - Clustrix Documentation". Clustrix, Inc. 
  10. ^ "Couchbase distributed database". Couchbase. 
  11. ^ "Druid distributed datastore/database". The Druid Community. 
  12. ^ "FoundationDB database". FoundationDB. Archived from the original on 2014-05-08. 
  13. ^ Clark, Jack. "NuoDB slurps European cash for database expansion" The Register. Feb. 26, 2014
  14. ^ "Basho Riak Distributed database". Basho. 
  15. ^ "OrientDB database". OrientDB. 
  16. ^ Margaret, Alyson (23 June 2015). "How Bitcoin and the blockchain are a transformative technology". Retrieved 23 July 2015. 
  17. ^ "Clusterpoint database distributed storage multi-datacenter replication". Clusterpoint. 
  18. ^ "Riak database multi-datacenter replication". Basho. 
  19. ^ Security, Networx. "Distributed Database". www.networxsecurity.org. Retrieved 2018-02-06. 

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