Database Reference
In-Depth Information
geological companies, and marketing-analysis firms are examples of organizations that use
analytical databases.
1.2.2 Characteristics of the database approach
• Data Abstraction — A data model is used to hide storage details and present the users
with a conceptual view of the database.
Programs refer to the data model constructs rather than data storage details
• Support of multiple views of the data — Each user may see a different view of the data-
base, which describes only the data of interest to that user.
• Sharing of data and multi-user transaction processing — Allowing a set of concurrent
users to retrieve from and to update the database.
Concurrency control within the DBMS guarantees that each transaction is correctly ex-
ecuted or aborted
Recovery subsystem ensures each completed transaction has its effect permanently recor-
ded in the database
OLTP (Online Transaction Processing) is a major part of database applications. This allows
hundreds of concurrent transactions to execute per second.
1.3 DATABASE MANAGEMENT SYSTEM
Database management system (DBMS) is a software system that is used to define, create,
and maintain databases. It assists in maintaining and utilizing large collections of data and
also provides various levels of access control to users
.
It allows uses to communicate with
databases. In other words, we can say that it is mediator between users and databases.
DBMS may have utilities software such as database designer tools, report writers and ap-
plication development tools. The various common examples of DBMS are Oracle, Access,
SQL Server, Sybase, DB2, FoxPro, Dbase etc.
A DBMS presents a logical view of the data to the users. How this data is stored and re-
trieved is hidden from the users. A DBMS ensures that the data is consistent across the
database and controls who can access what data.
DBMS software is installed on computer called data base server which hold databases.
Configuration (like processing capability and storage capacity) of server computer, size of
organization and volume of data will determine whether it is a single user or multi-user sys-
tem. In single user system only one user is allowed to access database at a time and whole
database resides on a single computer. User performs various tasks like designing of data-
bases, maintenance of database, writing application programs for systems and other related
activities.
