Why we need NoSQL Database?
Better to start with example. If a store is having 100k products to sell, and having 20 million hits per day,
- It is difficult to query each product every time from central database.
- Oracle is very costly to maintain in distributed environment.
- Also difficult to read and write at the same time.
With NoSQL Database,
- We can get better performance
- Easy to deploy and manage across continents
- Cost effective
It is not easy as these few points; there are many things to consider.
Also we need to have two-tier approach. For transactions, it is better to use JPA supported databases. For read only, it is better to use NoSQL Databases.
The software is like Clay. In the hands of Architect, it can take different shapes like tiles and pots.
For more information read http://en.wikipedia.org/wiki/NoSQL