Centralised and distributed databases

Centralised Database

Centralised Database

A single central database accessed by multiple users

+ Easier to organise, edit, query and backup

- Can be slower because of high usage / load

Distributed Database

Distributed Database

Database split into multiple files

+ Data access and retrieval faster at nearest points

- Can be slower accessing non local data

- Need to be ensure data is consistent / synchronised

Distributed Database

Vertical Partitioning

Split the database to improve speed

• Group commonly queried fields together• Physically closer together therefore faster to retrieve

Distributed Database

Horizontal Partitioning

Split the database according to a specific criteria

• Tables have exactly the same structure• Organise database geographically / by region

Replication

All data copied to all locations in the organisation

Data is processed on local copies of the database

Any changes copied to central database when low usage (e.g. night)

Central Index

Database index is held centrally, which then links to actual data

+ Don’t store all the data in the main database so it is not frequently updated

- May be a delay in retrieving data from actual database

Data Warehouse / Data MiningInvestigate

What is meant by a data warehouse

What is meant by data mining

CreditsHigher Information Systems – Using Information – Centralised and Distributed Databases

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