Monday, August 11, 2014

Advantages and Disadvantages of Distributed Databases

Advantages and Disadvantages of Distributed Databases over Centralized Databases / Relative Advantages of Distributed Databases / Disadvantages of Distributed Databases / Discuss the Advantages and Disadvantages of Distributed Databases / Advantages of Distributed Databases compared to Centralized Databases / Advantages and Disadvantages of Distributed Database Management System / Advantages and Disadvantages of Distributed Database System over Centralized Database System

Advantages of Distributed Database System

1. Increased reliability and availability – A distributed database system is robust to failure to some extent. Hence, it is reliable when compared to a Centralized database system.
2. Local control – The data is distributed in such a way that every portion of it is local to some sites (servers). The site in which the portion of data is stored is the owner of the data.
3. Modular growth (resilient) – Growth is easier. We do not need to interrupt any of the functioning sites to introduce (add) a new site. Hence, the expansion of the whole system is easier. Removal of site is also does not cause much problems.
4. Lower communication costs (More Economical) – Data are distributed in such a way that they are available near to the location where they are needed more. This reduces the communication cost much more compared to a centralized system.
5. Faster response – Most of the data are local and in close proximity to where they are needed. Hence, the requests can be answered quickly compared to a centralized system.
6. Reflects the organizational structure – Normally, database is fragmented into various locations wherever we have controls.
7. Secured management of distributed data – Various transparencies like network transparency, fragmentation transparency, and replication transparency are implemented to hide the actual implementation details of the whole distributed system. In such way, Distributed database provides security for data.
8. Robust – The system is continued to work in case of failures. For example, replicated distributed database performs in spite of failure of other sites.
9. Complied with ACID properties – Distributed transactions demands Atomicity, Consistency, Isolation, and Reliability.
10. Improved performance and Parallelism in executing transactions can be achieved.  

Disadvantages of Distributed Database Systems

1. Complex Software – Complex implementation. Costs more in terms of software cost compared to a centralized system. Additional software might be needed in most of the cases over a centralized system.
2. Increased Processing overhead – It costs many messages to be shared between sites to complete a distributed transaction.
3. Data integrity – Data integrity becomes complex. Too much network resources may be used.
4. Different data formats might be used – This may cost time.
5. Deadlock is difficult to handle compared to a centralized system.
6. May cause much more network traffic in case of write operation in a replicated form of distributed database.
7. Distributed System supported Operating System is required to implement distributed database system.
8. The data shared between sites over networks are vulnerable to attack. Hence, network oriented security protocols to be used based on the sensitivity of data shared.
9. More complex in terms database design – According to various applications, we may need to fragment a database, or replicate a database or both.
10. Handling failures is a difficult task. In some cases, we may not distinguish site failure, network partition, and link failure.

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