Components of a DBMS

Database Management System (DBMS)

           DBMSs are the technology tools that directly support managing organizational data. With a DBMS you can create a database including its logical structure and constraints, you can manipulate the data and information it contains, or you can directly create a simple database application or reporting tool.  Human administrators, through a user interface, perform certain tasks with the tool such as creating a database, converting an existing database, or archiving a large and growing database.  Business applications, which perform the higher level tasks of managing business processes, interact with end users and other applications and, to store and manage data, rely on and directly operate their own underlying database through a standard programming interface like ODBC. 

The following diagram illustrates the five components of a DBMS.


                                          

Database Engine:

        The Database Engine is the core service for storing, processing, and securing data. The Database Engine provides controlled access and rapid transaction processing to meet the requirements of the most demanding data consuming applications within your enterprise.Use the Database Engine to create relational databases for online transaction processing or online analytical processing data. This includes creating tables for storing data, and database objects such as indexes, views, and stored procedures for viewing, managing, and securing data. You can use SQL Server Management Studio to manage the database objects, and SQL Server Profiler for capturing server events.

Data dictionary:

       A data dictionary is a reserved space within a database which is used to store information about the database itself. A data dictionary is a set of table and views which can only be read and never altered.Most data dictionaries contain different information about the data used in the enterprise. In terms of the database representation of the data, the data table defines all schema objects including views, tables, clusters, indexes, sequences, synonyms, procedures, packages, functions, triggers and many more. This will ensure that all these things follow one standard defined in the dictionary. The data dictionary also defines how much space has been allocated for and / or currently in used by all the schema objects.A data dictionary is used when finding information about users, objects, schema and storage structures. Every time a data definition language (DDL) statement is issued, the data dictionary becomes modified.


A data dictionary may contain information such as:

  • Database design information
  • Stored SQL procedures
  • User permissions
  • User statistics
  • Database process information
  • Database growth statistics
  • Database performance statistics

Query Processor :

            A relational database consists of many parts, but at its heart are two major components: the storage engine and the query processor. The storage engine writes data to and reads data from the disk. It manages records, controls concurrency, and maintains log files.The query processor accepts SQL syntax, selects a plan for executing the syntax, and then executes the chosen plan. The user or program interacts with the query processor, and the query processor in turn interacts with the storage engine. The query processor isolates the user from the details of execution: The user specifies the result, and the query processor determines how this result is obtained.
The query processor components include

  • DDL interpreter
  • DML compiler
  • Query evaluation engine

Report writer:

         Also called a report generator, a program, usually part of a database management system, that extracts information from one or more files and presents the information in a specified format. Most report writers allow you to select records that meet certain conditions and to display selected fields in rows and columns. You can also format data into pie charts, bar charts, and other diagrams. Once you have created a format for a report, you can save the format specifications in a file and continue reusing it for new data.


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