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Big Data Analytics Articles
Page 111 of 135
Explain about two phase locking (2PL) protocol(DBMS)
Locking and unlocking of the database should be done in such a way that there is no inconsistency, deadlock, and no starvation.2PL locking protocolEvery transaction will lock and unlock the data item in two different phases.Growing Phase − All the locks are issued in this phase. No locks are released, after all changes to data-items are committed and then the second phase (shrinking phase) starts.Shrinking phase − No locks are issued in this phase, all the changes to data-items are noted (stored) and then locks are released.The 2PL locking protocol is represented diagrammatically as follows −In the growing phase transaction ...
Read MoreExplain attributes and the different types of attributes in DBMS?
Attributes are the properties which describe an entity. Example The attributes of student entity are as follows − Roll number Name Branch Age Types of attributes The different types of attributes are as follows − Composite attribute It can be divided into smaller sub parts, each sub part can form an independent attribute. For example − ...
Read MoreExplain the role of the Database Administrator in DBMS?
A database administrator (DBA) is a person or group in charge of implementing DBMS in an organization. The DBA job requires a high degree of technical expertise. DBA consists of a team of people rather than just one person.The primary role of Database administrator is as follows −Database designPerformance issuesDatabase accessibilityCapacity issuesData replicationTable MaintenanceResponsibilities of DBAThe responsibilities of DBA are as follows −Makes the decision concerning the content of the database.Plans the storage structure and access strategy.Provides the support to the users.Defines the security and integrity checks.Interpreter backup and recovery strategies.Monitoring the performance and responding to the changes in the ...
Read MoreWhat is data Abstraction in DBMS?
Data Abstraction is a process of hiding unwanted or irrelevant details from the end user. It provides a different view and helps in achieving data independence which is used to enhance the security of data.The database systems consist of complicated data structures and relations. For users to access the data easily, these complications are kept hidden, and only the relevant part of the database is made accessible to the users through data abstraction.Levels of abstraction for DBMSDatabase systems include complex data-structures. In terms of retrieval of data, reduce complexity in terms of usability of users and in order to make ...
Read MoreExplain the characteristics of DBMS?
There are so many characteristics of a database management system, which are as follows − A database management system is able to store any kind of data in a database. The database management system has to support ACID (atomicity, consistency, isolation, durability) properties. The Database management system allows so many users to access databases at the same time. Backup and recovery are ...
Read MoreWhat are different types of DBMS languages?
Once data is stored or filled it requires manipulation like insertion, deletion, updating, and modification of data. For these operations a set of languages are provided by the database management system (DBMS). So, the database languages are used to read, update and store data in the database.The different types of DBMS languages are as follows −Data Definition Language (DDL) − Create, Drop, Truncate, Rename.Data Manipulation language (DML) − Select, Insert, Delete, Update.Data Control Language (DCL) − Revoke, Grant.Transaction Control Language (TCL) − Rollback, Commit.The DBMS languages are pictorially represented as follows −Data Definition Language (DDL)It is a language that allows ...
Read MoreExplain about nested queries in DBMS
A nested query is a query that has another query embedded within it. The embedded query is called a subquery.A subquery typically appears within the WHERE clause of a query. It can sometimes appear in the FROM clause or HAVING clause.ExampleLet’s learn about nested queries with the help of an example.Find the names of employee who have regno=103The query is as follows −select E.ename from employee E where E.eid IN (select S.eid from salary S where S.regno=103);Student tableThe student table is created as follows −create table student(id number(10), name varchar2(20), classID number(10), marks varchar2(20)); Insert into student values(1, 'pinky', 3, ...
Read MoreWhat is tier-3 architecture in DBMS?
The overall design of the Database Management System (DBMS) depends on its architecture. A large amount of data on web servers, Personal Computers (PC) and other elements are linked with networks with the help of basic client or server architecture.PCs and workstations are part of Client architecture that are connected over the network. The architecture of DBMS depends on how the users are linked to the database.There are three kinds of DBMS Architecture, which are as follows −Tier-1 Architecture.Tier-2 Architecture.Tier-3 Architecture.Tier-3 ArchitectureThe 3-tier architecture contains one more layer between the client and the server.In this architecture, there is no direct ...
Read MoreWhat are the applications of DBMS?
The Database Management System (DBMS) is defined as a software system that allows the user to define, create and maintain the database and provide control access to the data.It is a collection of programs used for managing data and simultaneously it supports different types of users to create, manage, retrieve, update and store information.Applications of DBMSIn so many fields, we will use a database management system.Let’s see some of the applications where database management system uses −Railway Reservation System − The railway reservation system database plays a very important role by keeping record of ticket booking, train’s departure time and ...
Read MoreWhat are the DCL commands in DBMS?
Data control language (DCL) is used to access the stored data. It is mainly used for revoke and to grant the user the required access to a database. In the database, this language does not have the feature of rollback.It is a part of the structured query language (SQL).It helps in controlling access to information stored in a database. It complements the data manipulation language (DML) and the data definition language (DDL).It is the simplest among three commands.It provides the administrators, to remove and set database permissions to desired users as needed.These commands are employed to grant, remove and deny ...
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