Wikibooks: Design of Main Memory Database System/Overview of DBMS

• Format: Book
• Language: English
• Subjects: DML
• Online Access: https://en.wikibooks.org/wiki/Design_of_Main_Memory_Database_System/Overview_of_DBMS

Chapter 2 Introduction to Database Management Systems [[Table of Contents]] mdash Previous [[Introduction]] mdash Next [[Introduction to MMDB]] =2.1 Overview= The database management system (DBMS) is the software that handles storage and retrieval of data. Most of the DBMS present today are relational DBMS. This book concentrates only on relational database management systems. RDBMS has five main components Interface Drivers SQL Engine Transaction Engine Relational Engine Storage Engine Figure 1 contains DBMS components Memory layout and disk files associated with relational database management system. From early days of database system evolution disk is considered to be the backing store for the data to achieve durability. The architecture above applies for disk resident database systems (DRDB). Nowadays there are two different approaches other than DRDBs. They are Main memory databases (MMDB) – data is stored in main memory. Network Databases – data is stored in another host over the network. Most of the components in the DRDB system architecture above are present in main memory and network databases as well. =2.2 Driver Interfaces= A user or application program shall initiate either schema modification or content modification. These application requests are broadly classified by SQL as Data Definition Language (DDL) Data Manipulation Language (DML) and Data Control Language (DCL). DDL deals with schema modifications DML deals with content modifications DCL deals with user access and privilege modifications. If the application program is written in C/C++ it shall use ODBC drivers to connect to the DBMS or if it is written in Java it shall use JDBC drivers to connect to DBMS. Some vendors provide language specific proprietary interfaces. For example MySQL provides drivers for PHP Python etc. These drivers are built on top of SQL. They provide methods to prepare statements execute statements fetch results etc. =2.3 SQL Engine= This component is responsible for interpreting and executing the SQL query. It ...