Thursday, May 4, 2017

What is heterogeneous distributed DBMS

What is heterogeneous distributed DBMS? Heterogeneous distributed database example, why heterogeneous distributed DBMS

Heterogeneous Distributed DBMS

Distributed database is logically interrelated databases that are spread over multiple sites (servers usually at different geographic locations). Distributed DBMS is the software that handles or controls distributed databases efficiently.
In distributed database, each site has the following properties;

  • It runs on local DBMS software.
  • The database stored locally has a schema (structure).
  • A degree of autonomy on the data those are stored locally and partial autonomy on other sites etc.

A distributed DBMS is a heterogeneous DBMS if one or few or all of the following are true;

  • The sites at different location may use different DBMS software and application software. 
    • For example, site at Chennai may use Oracle while the site at New York may use SQL Server.
  • Databases that are stored locally at each server may have different structure. 
    • For example, a student table with the schema STUDENT(Regno, Name, Phone, Gender) will be stored at one site with the said schema and at the other with the schema STUDENT(Regno, Phone).
  • If either the DBMS software, or the schema, or the application software that uses the data is different at different sites, then it is hard for each site to know about other sites. But each site has full control over the local data.



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