Distributed Database Operating System II
A distributed database is a collection of multiple interconnected databases, which are spread physically across various locations that communicate via a computer network.
A distributed database management system (DDBMS) is a centralized software system that manages a distributed database in a manner as if it were all stored in a single location.
Advantages of the distributed database management system (DDBMS)
- Processor independence – the end-user is able to access available data and the user’s request is processed by any processor at the data location.
- More reliable – In case of database failures, the functioning of the system continues and maybe at a reduced performance.
- Better Response− If data is distributed in an efficient manner, then user requests can be met from local data itself, thus providing a faster response.
- Lower Communication Cost− In distributed database systems, if data is located locally where it is mostly used, then the communication costs for data manipulation can be minimized.
- Modular Development− If the system needs to be expanded to new locations or new units, the work simply requires adding new computers and local data to the new site and finally connecting them to the distributed system, with no interruption in current functions.
Disadvantages of the distributed database management system (DDBMS)
- Need for complex and expensive software− DDBMS demands complex and often expensive software to provide data transparency and coordination across several sites.
- Processing overhead− Even simple operations may require a large number of communications and additional calculations to provide uniformity in data across the sites.
- Data integrity– The need for updating data in multiple sites pose problems of data integrity.
- Increased storage and infrastructure requirements – multiple copies of data are required at different sites, thus requiring additional disk storage.
- Expensive – since it requires duplicated infrastructure to operate e.g., software, personnel, physical location, etc.
- Security – the probability of security lapses increases when copies of data are located at multiple sites.
Goals of the distributed database management system (DDBMS)
- Transparency – this hides implementation details from the user. It also allows the user to perceive the database as a single logical entity.
- Openness – Make it easier to build and change and also run on a different architecture.
- Reliability – a distributed system should be more reliable than a single system. This helps to solve:
- Need to maintain consistency
- Need to be secure
- Fault tolerance: need to mask failures, recover from errors.
- Performance – Performance loss due to communication delays should be as minimal and in case it happens, fast measures should be taken and the system should not tolerate faults.
- Scalability – Systems grow with time or become obsolete, this calls the need for techniques that require resources linearly in terms of the size of the system that is not scalable.