1) Databases in the collection are logically interrelated with each other. Often they represent a single logical database.
2) Data is physically stored across multiple sites. Data in each site can be managed by a DBMS independent of the other sites.
3) The processors in the sites are connected via a network. They do not have any multiprocessor configuration.
4) A distributed database is not a loosely connected file system.
5) A distributed database incorporates transaction processing, but it is not synonymous with a transaction processing system.
Features of a Distributed DBMS
- A distributed DBMS is a collection of logically related shared data.
- The data in a distributed DBMS is split into a number of fragments or partitions.
- Fragments may be replicated in a distributed system.
- Fragments/replicas are allocated to different sites.
- In a distributed system, the sites are linked by communications network.
- The data at each site is under the control of a DBMS.
- The DBMS at each site has its own right, that is, it can handle local applications independently.
- Each DBMS in a distributed system participates in at least one global application.