What is the difference between ddbms and rdbms?

Answer 1

DBMS (Database Management System) is a genaral term for any system used to store, manage, and retrieve from a collection of data. It can be something as simple as a box of index cards, a collection of computer documents or spreadsheets, or more commonly a software program designed specifically for managing collections of data. Most DBMSs today are RDBMSs and most DDBMSs are based on RDBMSs. The RDBMS (Relational DBMS) is based on a Computer Science concept known as relations. The purpose of the RDBMS is to organize the information logically (for humans) and to efficiently store and retrieve the information (by computers). Typically, tables are defined for each class of thing for which data is to be kept. Tables contain a row for each unique thing belonging to the table's class. Each row contain facts directly related to the thing and a unique identifer (name, code, number, etc.) that distinguishes each thing from all other things in the same class. A row may contain cross-references to the unique identifiers of one or more rows in other tables to show relationships that exist between things. Tables provide the logical organization for human use, and the unique identifiers and cross-reference relations provide the RDBMS system the technical mechanism to efficiently store and retrieve all the information in the database. For example, a Sales database might contain Customers, Products, Orders, and OrderItems tables defined as follows: Customer - ID:CustomerId Facts:Name,Address,Telephone,ContactName Products - ID:SKUNumber Facts:Price,QuantityOnHand,Description Orders - ID:OrderID CrossRefs:CustomerID Facts:OrderDate,PaymentStatus OrderItems - ID:OrderItemID CrossRefs:OrderID,ProductID Facts:Quantity,Price The DDBMS (Distributed DBMS) simply means the DBMS (which is usually also an RDBMS) data is stored on more than one computer. The computers may be physically in different parts of the world, connected by the internet or other type of network. The DDBMS software allows you to manage the database as one whole collection of data even though different parts of the data are distributed across multiple machines. If the data is updated more often than it is retrieved, each machine could store a different subset of the database most likely to be retrieved from that location (European Customers stored on the database server in London while U.S. Customers are on the database server in Seattle). So the DDBMS must know how to gather the data over the network from different servers, when a user runs a report of all Customers with sales greater than $1,000,000. If the data is retrieved more often than it is updated, all data updates done in one location could be replicated (automatically copied) to all of the other database servers in the system. This allows for faster retrieval of any information from any location. The efficiency of a DDBMS depends on making good decisions about the physical storage and replication plan (if, how often, and where to) for each subset of data.