Adbms 28 components of distributed database system
- 1. Advance Database Management Systems :28 Components of Distributed Database System Prof Neeraj Bhargava Vaibhav Khanna Department of Computer Science School of Engineering and Systems Sciences Maharshi Dayanand Saraswati University Ajmer
- 2. Distributed Databases • In this architecture, the database is distributed, possibly with replication, among several relatively autonomous sites. • The distribution is transparent to the user, who does not need to specify where the data is located (location transparency). • A distributed system can be homogeneous or heterogeneous.
- 3. Homogeneous vs heterogeneous • In a homogeneous system, all nodes use the same hardware and software for the database system. • In a heterogeneous system, nodes can have different hardware and/or software. • Since a homogeneous system is much easier to design and manage, a designer would normally choose such a system. • Heterogeneous systems usually result when individual sites make their own hardware and software decisions, and communications are added later, which is the norm.
- 4. Homogeneous vs heterogeneous • The designer then has the task of tying together the disparate systems. • In a heterogeneous system, translations are needed to allow the databases to communicate. • Since location transparency is a major objective, the user at a particular site makes requests in the language of the database management system at that site. • The system then has the responsibility of locating the data, which might be at another site that has different hardware and software.
- 5. Homogeneous vs heterogeneous • The request might even require coordination of data stored at several sites, all using different facilities. • If two sites have different hardware but the same database management systems, the translation is not too difficult, consisting mainly of changing codes and word lengths. • If they have the same hardware but different software, the translation is difficult, requiring that the data model and data structures of one system be expressed in terms of the models and structures of another. • For example, if one database is relational and the other uses the semistructured model, objects must be presented in table form to users of the relational database. • In addition, the query languages must be translated. The most challenging environment involves different hardware and software. • This requires translation of data models, data structures, query languages, word lengths, and codes.
- 7. Data communications (DC) component. • Data communications (DC) component. The data communications component is the software at each node that links it to the network. • This DC component includes a complete description of the network’s nodes and lines. • For each node, it identifies processing performed, storage capacity, processing power, and current state. • For each link, it identifies the nodes it connects, type of link, bandwidth, protocols required, and the current state of the link.
- 8. Local database management (LDBMS) component • Local database management (LDBMS) component. • The local database management component functions as a standard database management system, responsible for controlling the local data at each site that has a database. • It has its own data dictionary for local data, as well as the usual subsystems for concurrency control, recovery, query optimization, and so on.
- 9. Global data dictionary (GDD). • Global data dictionary (GDD). The global data dictionary is a repository of information about the distributed database. • It includes a list of all data items with their location and other information about data stored anywhere in the distributed system.
- 10. Assignment • Explain Homogeneous vs heterogeneous distributed databases • What are the components of a distributed database system