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    Components of DBMS

    A database management system (DBMS) consists of various components. Each component shows a significant act in the database management system environment.

    The major components of a database management system are:

    Components of DBMS
    Data

    Data is an essential component of the DBMS. The main purpose of DBMS is to execute the data. In DBMS, data is stored in the system is partitioned into one or more databases. A database is both integrated and shared.

    By ‘integrated’, we define that the database might be thought of as a consolidation of a few distinct data files with any repetition between those records partly or entirely removed.

    By ‘shared’, we mean that individual portion of data in the database can be shared among several distinctive users, in the sense that each of those users may have access to the similar part of data (and may use it for numerous purposes). Such sharing is a result of the fact that the database is integrated.

    Components of DBMS
    Hardware

    The hardware consists of the secondary storage volumes disks, drums, etc. on which the database resides, together with the associate devices, control units, channels, and so forth.

    Software
    • The main component of a Database management system is the software. It is the set of programs that is used to manage the database and to control the overall computerized database.
    • The DBMS software provides an easy-to-use interface to store, retrieve, and update data in the database.
    • This software segment is sufficient for understanding the Database Access Language and changes it into actual database commands to execute or run them on the database.
    Procedures

    Procedures refer to general guidelines to use a database management framework. This contains procedures to set up and introduces a DBMS, to login and logout of DBMS programming, to address databases, to take reinforcement, making records, etc.

    Database Users

    There are three classes of users:

    Application Programmer

    The application programmer answerable for writing software applications that use the database, normally in a language consisting of COBOL or PL/1, to meet the person requirement. These application programs operate on the data in all usual ways: retrieving information, creating new data, deleting, or changing existing data.

    End-Users

    The second class of the user is the end-users, accessing the database from a terminal.

    There are two-types of End-users:

    • Casual Users: Casual users are trained in the use of online query language and access data by entering queries at terminals.
    • Naïve Users: Naïve users access data through application programs that have been written for them.
    DBA (Database Administrator)

    DBA is a person or set of persons answerable for overall control of the database.

    This administrator needs both technical and managerial skills. Key functions of a database administrator are:

    Components of DBMS
    • Interaction with users and all levels of management.
    • Supervision of all database maintenance.
    • Design and coordination of data security measures to restrict unauthorized access.
    • Design of database files and supervision of a database dictionary and user’s manual, which gives standardized procedures for access to the database.
    • Responsibility and control overall database documentation.
    • Overseeing all database activities to ensure prompt system response, satisfactory user support, and data security.
    Query Processor

    The query processor change customer queries into a grouping of low-level rules. It is the usage of to interpret the online customer query and modify it into a useful collection of functions in a structure capable of being transmitted to the run-time data supervisor for execution. The query processor utilizes the data dictionary to find out the architecture of the significant part of the database and makes use of this information in converting the query and getting and perfect plan to create the database.

    Run Time Database Manager

    Run time database manager is the principal programming elements of the DBMS, which associates with customer-submitted application programs and queries. It handles the database create at run time. It converts functions in customer’s queries coming directly through the query processor or indirectly through a function program from the user’s logical view to a physical file structure. It accepts queries and determines the outside and conceptual schemas to decide what conceptual facts are needed to satisfy the person’s request. It authorizes constraints to keep up the consistency and integrity of the data, just as its security. It executes backing and recovery operations.

    Run time database manager is sometimes described to as the database control system and has the following components:

    Authorization control: The authorization control module examines the authorization of users in phrases of numerous privileges to users.

    Command processor: The command processor performs the queries passed by the authorization control module.

    Components of DBMS

    Integrity checker: It examines the integrity constraints so that only valid information may be entered into the database.

    Query optimizer: The query optimizers determines an optimal method for query execution.

    Transaction Manager: The transaction manager performs the required processing of functions it receives from transactions.

    Scheduler: The scheduler is responsible for ensuring that concurrent operations at the database proceed without conflicting with one another. It controls the associative order in which transaction operations are executed.

    Data Manager: The data manager is liable for the real managing of data within the database.

    This module has the following two components:

    Recovery Manager:

    The recovery manager ensures that the database remains in a consistent state inside the presence of failures.

    It is responsible for:

    1. Transaction commit and abort operations
    2. Maintaining a log
    3. Restoring the framework to a consistent state after a crash
    Buffer Manager

    The buffer manager is liable for the transfer of records between the primary memory and secondary storage (including disk or tape). It brings in pages from the disk to the primary memory as needed in response to read client requests. The buffer manager is sometimes described as the cache manager.

    DML Processor

    Using a DML compiler, the DML processor converts the DML statements installed in an application software into standard function calls within the host language. The DML compiler converts the DML statements written in a bunch programming language into item code for database access. The DML processor needs to have interaction with the query processor to generate the right code.

    DDL Processor

    Using a DDL compiler, the DDL processor converts the DDL statements into a series of tables, including metadata. These tables include the metadata regarding the database and are in a structure that can be used by other components of the DBMS. These tables are them saved in the system catalog, while control data is stored in datafile headers.

    The DDL compiler processes schema definitions, specified within the DDL and stores description of the schema (metadata) in the DBMS framework catalog. The system catalog contains information such as the names of data files, record items, storage details of each data record, mapping data amongst schemas, and constraints.

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