What are the different strategies for placing the data in distributed database?, different data allocation metrics followed in distributed database, how data are placed in a distributed database?
Different strategies for placing data in distributed database
A distributed database implementation
follows one of the following data placement strategies for ease of access. The selection
is influenced by many factors like the locality, reliability, performance,
storage and communication costs.
|
Strategy
|
Description
|
|
Centralized
|
Database tables
are stored in a single location/single site (server). All the other sites have
to forward the request to the central site for accessing data.
|
|
Fragmented (Partitioned)
|
Database tables
are fragmented (either vertically or horizontally or both) and different
fragments are stored in different sites.
|
|
Complete replication
|
Database tables
are replicated (duplicated) fully into two or more copies and each copy is
stored in different sites.
|
|
Selective replication
|
Among set of
tables, certain tables are made into multiple copies and stored in different
sites. The tables that are most frequently accessed will be replicated.
|
|
Hybrid
|
It is the mix of
all. Most of the distributed databases follow this strategy. Here, some of
the tables replicated, some of the tables fragmented, etc.
|
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