Oracle Interview Questions and Answers

Employing Oracle DBA specialists is becoming commonplace as businesses seek to satisfy their and their clients’ needs and aspirations. You’ve come to the correct site if you’re seeking Oracle interview questions. Experts with over fifteen years of Oracle DBA expertise have developed these Oracle Apps interview questions and answers. Let us review some of the most typical questions asked during an Oracle DBA technical interview. Explore our Oracle course syllabus that is blended with theory and hands-on.

What is Oracle?

The database server Oracle uses a methodical approach to data management. In a multi-user setting, it enables users to save and retrieve related data so that multiple users can access the same data at once. All of this is done while giving excellent performances. In addition, a database server offers effective failure recovery options and blocks unwanted access. A database replica made from a primary database backup is known as a standby database.

What is an Oracle database?

Oracle provides software for creating and managing Oracle databases. Information about users, systems, and controls is kept in the database’s logical and physical structures. The Oracle Database Server is the program that oversees the database. The Oracle Database System refers to both the actual database and the software that operates Oracle.

The data is kept in memory for faster access in a database buffer cache. All database modifications are monitored and recorded in the redo logs. A data guard ensures high availability and data security, while a control file records the physical layout of the database.

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What are the Oracle DBA characteristics?

Oracle DBA has a main storage structure for physical and logical storage. It has a grid architecture that is fully ACID compliance and the data will be stored as data blocks, extents, tablespaces, and segments.

Explain the Oracle Index.

An optional structure that can be added to a table to provide direct access to rows and improve data retrieval performance is called an index. A table’s columns on which an index can be made are one or more.

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Why is the index used?

Indexes are used to make data easier to access. It is also employed to improve retrieval data performance. Finding the necessary information quickly without having to look through every row is helpful.

Who is in charge of keeping the indexes updated?

Oracle can use and manage indexes. Every time there is a change in the table data, it automatically distributes the data into the appropriate indexes.

What kinds of databases are there on the market?

The market is filled with a wide variety of databases. Oracle, IBM db2, Microsoft SQL Server, Microsoft Access, MySQL and SQLite, PostgreSQL, and MariaDB are the most widely used databases.

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Which physical parts make up the Oracle database?

There are five physical parts to an Oracle database: data files, control files, redo log files, password files, and parameter files.

What functions do DBAs perform?

A DBA has the power to change any environment variable or privilege that has been granted to another user, as well as to add new users and remove current ones.

Manage database storage
Administer users and security
Manage schema objects
Monitor and manage database performance
Perform backup and recovery
Schedule and automate jobs

What are the various types of Oracle database objects?

Tables, views, indexes, synonyms, sequences, and tablespaces are the various types of Oracle database objects.

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Explain the term ‘synonym’ in Oracle

An identifier that can be used in an SQL statement to refer to another database entity is called a synonym. For a synonym, other kinds of database objects can be made, including tables, views, and sequences. Explore the differences between a view and a materialized view.

Describe the various synonym types.

Synonyms come in two varieties: public and private.

Public synonyms are not included in any schemas. Any database user can use a public synonym.
A private synonym is a part of a particular schema. Put another way, a private synonym is only accessible by the owner.

What are the various types of backups in Oracle?

The four main types of backups in Oracle are

Cold Backup
Hot Backup
Import – Export Backup
RMAN Backup

What do cold and hot backups mean?

Because hot backups occur while the database is operational, they are often referred to as online backups. Cold backups, also known as offline backups, are those in which the backup can only occur after the database is shut off.

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Data Files: What Are They?

Within a computer system, data files store and arrange several kinds of information, such as text, numbers, photos, and more. These files are necessary for software programs and systems to efficiently access and handle data.

What is the process for converting an init.ora file to a spfile?

To convert an init.ora file to a ‘spfile’, we must first generate the ‘spfile’ using the ‘pfile’ command, then stop the instance and restart it.

Which kinds of SQL statements are there?

The following are the five categories of SQL statements:

Data Definition Language (DDL)
Data Manipulation Language (DML)
Transactional Control Language (TCL)
Session Control Language (SCL)
System Control Language (SysCL)

Data Normalization: What Is It?

In database architecture, data normalization is the act of arranging and structuring data to reduce dependencies and redundancies. It adheres to a set of standards and directives to guarantee data integrity and boost database performance. By dividing data into smaller, more manageable tables and creating linkages between them, data normalization aims to remove anomalies and redundancies.

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A Control File: What Is It?

A binary file is necessary to launch and maintain the database and contains information about its physical layout.

Information like this can be found in a control file.

Data file

Database name

Redo file name

Locations of associated data files and redo files.

Timestamp of database creation.

Current log sequence number

Checkpoint information

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How can a lost control file be recovered?

How to retrieve a deleted control file:

Select NOMOUNT when starting the database.
Using the CREATE CONTROLFILE command, create the control file from the control file backup and save it in the appropriate location.
Install the database.
Retrieve the database.
Get the database open.

By “redo logo files,” what do you mean?

Keeping track of all data changes is the primary goal of the redo log. Corrections from the redo log can be done if a problem prevents personalized data from being permanently written to data files, guaranteeing that the effort is never lost.

Define file parameters

A text file containing a list of initialization parameters and their values is called a parameter file. The parameters used for initialization are specified in a parameter file unique to your installation.

What does the Recovery Catalogue mean to you?

The metadata that RMAN oversees for data restoration and recovery procedures is stored in a database structure called the recovery catalog. Recovery catalogs contain the metadata that RMAN uses for the reinstallation and repair procedures. Even if the target control file and its backups are deleted, the RMAN metadata will still be present in the recovery catalog.

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Explain what system tablespace is and why it matters.

The system tablespace is produced during the database creation process. This tablespace is utilized to generate various database objects since it holds all of the data dictionary tables. The system tablespace needs to stay up to date for the database to function effectively.

What is the database version location?

You can use the following actions to find the version of an Oracle database:

Use a tool like SQL*Plus to establish a connection to the Oracle database.
Once connected, type “SELECT * FROM V$VERSION” in the query.
Run the query to obtain the database’s version information.
The database version’s details, including the Oracle release number and other version-specific data, will be shown in the outcome.

A Sequence: What Is It?

A sequence generates a sequential set of distinct numbers for numerical columns in database tables. If we wish to systematically insert data into a column, we can utilize the sequence.

What does the Oracle table definition mean?

The table is the initial physical item in a database. Oracle uses tables in a database to partition data into rows and columns. The table is the initial physical item in a database.

In SQL terminology, what do you mean by a view?

Any view can have a query added to it to define particular table rows and columns. One kind of virtual table is perspective. Two sorts of views are available: read-write and read-only.

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What are the benefits of utilizing View, please?

The benefits of employing a table view are

It is a portion of a table’s contents.
It keeps track of intricate queries.
It can combine several tables into a single one.
It takes up very little room.
It offers several viewpoints on the facts.

What do you mean by tablespace in Oracle terms?

A tablespace is a type of logical storage where related logical structures are grouped. All of the objects in the database will be arranged according to their logical structure.

How much time does it take to generate the SYSTEM tablespace?

A tablespace called SYSTEM is present in every Oracle database and is created automatically at database creation. A data dictionary table for the complete set of data is also included.

What connection exists between data files and tablespace?

There are one or more tablespaces in each database, and each tablespace is further partitioned into one or more data files.

How is the materialized view put to use?

Condensed sets of data from base tables that have been compiled, grouped, or summarised are called materialized views. Data centers and decision-making systems frequently employ them.

What does the SELECT statement intend to accomplish?

A database table’s unique values can be retrieved using the SELECT statement according to the specifications specified in a SQL query.

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How may a portion of the name be compared instead of the full name?

We employ the LIKE operator, which acts as a database’s regex engine, to compare several sections.

What keyword should I use to extract unique records from a table?

The user will choose distinct values from a database table by using the SELECT DISTINCT function.

What is the keyword to retrieve sorted records from a table?

The data is sorted using the term ‘ORDER BY.’ Your program receives the sorted results back from it.

What is the keyword to extract the total records from a table?

To determine the total number of records in a table, use the COUNT keyword.

What does the term GROUP BY mean?

The sum for each distinct group value cannot be found without the aggregate function GROUP BY, which is similar to SUM, MULTIPLE, and so forth.

What advantages do ORDBMSs offer?

The items can be kept just as they are in an ORDBMS. It is possible to integrate an object-oriented programming language with the DBMS language. It is even possible for the language to be the same as the application’s, so the programmer is not required to have two representations of his objects.

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Which tasks are typical for an Oracle DBA?

Among the responsibilities of an Oracle DBA are the following:

Setting up Oracle software
Building Databases in Oracle
Upgrading the software and database to the latest versions
launching and stopping the database
Controlling the storage structures in the database
Controlling users and security
Taking care of schema elements like tables, views, and indexes
generating backups for databases and carrying out recovery as required
keeping an eye on the database’s health and acting to avoid or fix issues when they arise
Tracking and fine-tuning performance

A single DBA may be able to manage each of these responsibilities in a small-to-midsize database environment. In large company installations, the full responsibility is sometimes divided among several DBAs, each with a specialist area named Database Security Administrator or Database Tuning Expert.

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A Dual Table: What Is It?

The dual table of user SYS is accessible to all users. It has one “columnDummy” and one row with the value X. The dual table is useful when you wish to return a value only once. The value may not come from a database containing user data; instead, it may be a constant, pseudocolumn, or expression.

What differentiates COUNT (*), COUNT (expression), and COUNT (distinct expression) from one another? (Where expression is the name of any ‘Table column’)?

COUNT (*): returns a table’s worth of rows, including duplicates and rows with null values in any column.

COUNT (EXP): Provides the total number of non-null values in the expression-identified column.

COUNT (DISTINCT EXP): Provides the total number of distinct, non-null values in the expression-identified column.

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What Kinds of Sub-Queries Are There?

A SELECT statement embedded in another SELECT statement’s clause is called a subquery. You can include a subquery in the FROM and WHERE clauses.

Tips for utilizing subqueries:

Place subquestions inside parentheses.
Subqueries should be positioned to the right of the comparison condition.
When using single-row subqueries, use single-row operators; when using multiple-row subqueries, use multiple-row operators.

There are many kinds of subqueries:

Subqueries with a single row returned from the inner select statement are known as single-row subqueries. The comparison operators for a single row are =, >, >=, \, \=, <>.
Multiple-row subqueries are subqueries that return more than one row from the inner Select statement. There are also multi-column subqueries that return a multitude of columns from the inner select expression. Operators include, for example, IN, ANY, and ALL.

The level of Oracle Apps technical interview preparation determines how easy or difficult the procedure appears. The Oracle interview questions are typically easy to medium level. Multiple interview rounds, however, may make the process difficult for certain applicants. With any luck, these Oracle Apps technical interview questions and interviews will assist you during your technical rounds at major companies. Get expertise in our Oracle DBA training in Chennai and grab a chance for a promising career.