Important considerations in distributed database over Centralized database
- Data allocation - We need to know the answers for the following questions; What to store? Where to store? and How to store?
- Data fragmentation - It is about, How one should organize the data?
- Distributed queries and transactions - We must find a way to handle the data using queries and to handle transactions which are happening in multiple distributed sites (Here site means a server).
- The data should be available in or near a site where it is needed most.
- The storage of data in a site should increase the availability and reliability of data.
- The strategy chosen for data allocation should increase the performance. That is, some of the drawbacks like bottleneck problem of central server concept or limited usability of data should be avoided.
- The idea should reduce the cost involved in storage and manipulation of data
- There should be a much reduced traffic or utilization of network. It should also ensure that there should never be a unnecessary use of network provided the data available near.
2. Data fragmentation
- Horizontal fragmentation
- Primary Horizontal fragmentation
- Derived Horizontal fragmentation
- Vertical fragmentation
- The identification of the location of requested data,
- A protocol to fetch the data, and
- A way to organize the data, if it was spread over multiple sites.
Further discussions on these considerations will be soon.