Related Articles on Database. In this design alternative, at each site, one copy of all the database tables is stored. Wrappers have been used ubiquitously in the industry as the approach for doing this. Data across constituent databases may be related but different. Characteristics of Distributed Database Management System.

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In a homogeneous system, all sites use the same DBMS product. In a heterogeneous system, sites may run different DBMS products, which need not be based on the same underlying data model, and so the system may be composed of relational, network, hierarchical and object-oriented DBMSs.

Homogeneous systems are much easier to design and manage. This approach provides incremental growth, making the addition of a new site to the DDBMS easy, and allows increased performance by exploiting the parallel processing capability of multiple sites. Heterogeneous system usually result when individual sites have implemented their own database and integration is considered at a later stage. In a heterogeneous system, translations are required to allow communication between different DBMSs.

The system then has the task of locating the data and performing any necessary translation. If the DBMS products are different, the translation is complicated, involving the mapping of the data structure in one data model to the equivalent data structures in another data model. For example, relations in the relational data model are mapped to records and sets in the network model. If both the hardware and software are different, then these two types of translation are required.

This makes the processing extremely complex. The typical solution use by some relational systems that are part of a heterogeneous DDBMS is to use gateways, which convert the language and model of each different DBMS into the language and model of the relational system.

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Distributed database

A database user accesses the distributed database through: Local applications applications which do not require data from other sites. Global applications applications which do require data from other sites. A homogeneous distributed database has identical software and hardware running all databases instances, and may appear through a single interface as if it were a single database. A heterogeneous distributed database may have different hardware, operating systems, database management systems, and even data models for different databases. Homogeneous Distributed Databases Management System[ edit ] In homogeneous distributed database, all sites have identical software and are aware of each other and agree to cooperate in processing user requests.


Distributed DBMS - Database Environments

They are integrated by a controlling application and use message passing to share data updates. Heterogeneous Database In a heterogeneous distributed database, different sites have different operating systems, DBMS products and data models. Architecture of Heterogeneous Database The underlying DBEs of a heterogeneous system are different in nature and may provide different interfaces to the outside world. One of the first challenges in integrating heterogeneous DBEs is to hide the difference in the interfaces these systems expose. Wrappers have been used ubiquitously in the industry as the approach for doing this.



Next Page In this part of the tutorial, we will study the different aspects that aid in designing distributed database environments. This chapter starts with the types of distributed databases. Distributed databases can be classified into homogeneous and heterogeneous databases having further divisions. The next section of this chapter discusses the distributed architectures namely client — server, peer — to — peer and multi — DBMS. Finally, the different design alternatives like replication and fragmentation are introduced.

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