Distributed database Management Systems (Resembling Setups)

Resembling Setups

• Distributed Files: A collection of files stored on different computers of a network; not a DDBS
• DDBS is logically related, common structure among files, and accessed via same interface
• Multiprocessor System: multiple processors that share some form of memory

Shared Everything Tight Coupling

Shared Everything Loose Coupling

Shared Nothing

• DDBS is also different from a centralized system having C/S system involving network

 

Reasons for DDBS

• Local units want control over data.
• Consolidate data for integrated decisions
• Reduce telecommunication costs.
• Reduce the risk of telecommunication failures.

Promises of DDBSs

Transparency

• Data Independence
• Two types, Logical Data Independence and Physical Data Independence
• A transparent system hides the implementation details from its users

Network Transparency

• User should not only be free from network management activities rather it should be unaware of even existence of the network
• Location Transparency and Naming Transparency