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Top 100 Oracle Interview Questions and Answers

Top 100 Oracle Interview Questions and Answers

Contents show

1. What is Oracle Database?

Answer: Oracle Database is a relational database management system (RDBMS) developed by Oracle Corporation. It stores and manages data in a structured format and provides advanced features like scalability, security, and high availability.


2. Explain ACID properties in the context of Oracle transactions.

Answer: ACID stands for Atomicity, Consistency, Isolation, and Durability. In Oracle transactions, Atomicity ensures that all changes are made as a single unit. Consistency ensures that data remains valid during transactions. Isolation ensures transactions are isolated from each other, and Durability guarantees that committed changes are permanent.


3. What is a primary key constraint in Oracle?

Answer: A primary key constraint in Oracle ensures that a column or set of columns uniquely identifies each row in a table. It enforces data integrity and automatically creates a unique index on the specified columns.


4. How do you create a new user in Oracle?

Answer: To create a new user in Oracle, you can use the CREATE USER SQL statement. For example:

CREATE USER new_user IDENTIFIED BY password;

Replace new_user with the username and password with the user’s password.


5. Explain the purpose of the Oracle Data Dictionary.

Answer: The Oracle Data Dictionary is a set of tables and views that store metadata and information about the database. It provides essential details about tables, columns, constraints, users, privileges, and more. It is crucial for database administration and querying metadata.


6. What is a stored procedure in Oracle?

Answer: A stored procedure in Oracle is a precompiled collection of one or more SQL statements. It is stored in the database and can be executed as a single unit. Stored procedures are used for code reusability, security, and performance optimization.


7. How can you retrieve the top N rows from a table in Oracle?

Answer: To retrieve the top N rows from a table in Oracle, you can use the ROWNUM or FETCH FIRST clause. For example:

Using ROWNUM:

SELECT * FROM your_table WHERE ROWNUM <= N;

Using FETCH FIRST:

SELECT * FROM your_table FETCH FIRST N ROWS ONLY;

8. Explain the purpose of the Oracle SQL*Plus tool.

Answer: SQL*Plus is a command-line tool provided by Oracle for interacting with Oracle databases. It allows users to execute SQL queries, scripts, and PL/SQL code, as well as perform database administration tasks. It is a powerful tool for database development and management.


9. What is normalization in the context of database design?

Answer: Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. It involves breaking down tables into smaller, related tables and establishing relationships between them using keys. The goal is to eliminate data anomalies and ensure efficient data storage.


10. How do you create a backup of an Oracle database?

Answer: You can create a backup of an Oracle database using Oracle Recovery Manager (RMAN) or by exporting data using tools like Data Pump (expdp). RMAN provides a comprehensive backup and recovery solution, while Data Pump is used for logical backups.


11. Explain the concept of a foreign key in Oracle.

Answer: A foreign key in Oracle is a column or set of columns in a table that establishes a link between two tables. It enforces referential integrity by ensuring that values in the foreign key match values in the primary key of another table.


12. How can you add a new column to an existing table in Oracle?

Answer: To add a new column to an existing table in Oracle, you can use the ALTER TABLE statement. For example:

ALTER TABLE your_table
ADD new_column datatype;

Replace your_table with the table name, new_column with the new column name, and datatype with the data type of the column.


13. Explain the role of the Oracle DBA (Database Administrator).

Answer: The Oracle DBA is responsible for managing and maintaining Oracle databases. Their tasks include installation, configuration, performance tuning, security, backup and recovery, user management, and ensuring the overall health and availability of the database system.


14. What is an Oracle sequence, and how is it used?

Answer: An Oracle sequence is an object that generates a series of unique numeric values. It is often used to generate primary key values for tables. Sequences are independent of transactions and can be shared among multiple users.


15. How do you update data in an Oracle table?

Answer: To update data in an Oracle table, you can use the UPDATE statement. For example:

UPDATE your_table
SET column1 = value1, column2 = value2
WHERE condition

;

Replace your_table with the table name, column1, column2, etc., with the columns to update, and value1, value2, etc., with the new values. The WHERE clause specifies which rows to update based on a condition.


16. Explain the concept of indexing in Oracle.

Answer: Indexing in Oracle involves creating data structures that provide faster access to rows in a table. Indexes are used to speed up data retrieval operations such as SELECT statements. Oracle automatically creates indexes for primary key and unique constraints.


17. What is the purpose of the Oracle listener?

Answer: The Oracle listener is a process that listens for incoming client connection requests and establishes network connections to the database. It plays a crucial role in enabling communication between clients and the Oracle database server.


18. How can you find duplicate rows in an Oracle table?

Answer: To find duplicate rows in an Oracle table, you can use the GROUP BY clause with the HAVING clause. For example:

SELECT column1, column2
FROM your_table
GROUP BY column1, column2
HAVING COUNT(*) > 1;

This query groups rows by specified columns and selects those groups with a count greater than one.


19. What is an Oracle view, and why is it used?

Answer: An Oracle view is a virtual table created by defining a query on one or more base tables. It does not store data but provides a logical representation of data from one or more tables. Views are used for data security, simplifying complex queries, and encapsulating business logic.


20. Explain the concept of a database trigger in Oracle.

Answer: A database trigger in Oracle is a set of actions that are automatically executed in response to a specific event, such as an INSERT, UPDATE, or DELETE operation on a table. Triggers are used to enforce data integrity, audit changes, or perform custom actions.


21. How do you remove a table in Oracle?

Answer: To remove a table in Oracle, you can use the DROP TABLE statement. For example:

DROP TABLE your_table;

Replace your_table with the name of the table you want to delete. Be cautious when using this statement, as it permanently deletes the table and its data.


22. Explain the concept of a PL/SQL cursor in Oracle.

Answer: A PL/SQL cursor in Oracle is a temporary work area used to retrieve and manipulate data from a result set. It allows developers to process rows one at a time, making it useful for looping through query results and performing operations on each row.


23. How can you retrieve the current date and time in Oracle?

Answer: You can retrieve the current date and time in Oracle using the SYSDATE function. For example:

SELECT SYSDATE FROM DUAL;

This query returns the current date and time.


24. What is the purpose of the Oracle COMMIT statement?

Answer: The COMMIT statement in Oracle is used to permanently save changes made during the current transaction to the database. It makes the changes permanent and releases locks, allowing other users to see the changes.


25. Explain the concept of a database schema in Oracle.

Answer: A database schema in Oracle is a logical container for database objects such as tables, views, indexes, and procedures. It provides a way to organize and manage database objects and control access to them.


26. How can you find the version of Oracle Database you are using?

Answer: You can find the version of Oracle Database by executing the following SQL query:

SELECT * FROM v$version;

This query retrieves version information from the v$version view.


27. What is the purpose of the Oracle SQL Developer tool?

Answer: Oracle SQL Developer is a graphical tool for database development tasks. It provides features for querying databases, designing tables, managing PL/SQL code, and performing various administrative tasks. It is a user-friendly environment for Oracle database developers.


28. Explain the concept of database normalization forms.

Answer: Database normalization forms are a series of rules that guide the process of designing a relational database. They help in organizing data to minimize redundancy and maintain data integrity. The common forms include First Normal Form (1NF), Second Normal Form (2NF), and Third Normal Form (3NF).


29. How can you prevent SQL injection in Oracle?

Answer: To prevent SQL injection in Oracle, use parameterized queries or bind variables in your SQL statements. Avoid concatenating user input directly into SQL queries. Parameterized queries ensure that user input is treated as data and not executable SQL code.


30. What is the purpose of the Oracle Data Pump utility?

Answer: Oracle Data Pump is a tool for exporting and importing

data and metadata between Oracle databases. It provides efficient methods for moving large volumes of data and is commonly used for backup, migration, and data transfer tasks.


31. What is an Oracle sequence, and how is it used?

Answer: An Oracle sequence is an object that generates a series of unique numbers. It is often used to generate primary key values in tables to ensure uniqueness and maintain order.

Example of creating a sequence:

CREATE SEQUENCE your_sequence
START WITH 1
INCREMENT BY 1;

32. Explain the purpose of the Oracle RMAN utility.

Answer: Oracle Recovery Manager (RMAN) is a utility for managing backup and recovery operations in Oracle databases. It allows you to create backups, restore data, and recover the database in the event of data loss or corruption.


33. What is an Oracle index-organized table (IOT)?

Answer: An index-organized table (IOT) in Oracle is a type of table that is stored in a B-tree index structure. It is primarily used for scenarios where data retrieval by the primary key is the most common access pattern. IOTs offer improved query performance for such use cases.


34. Explain the purpose of the Oracle Data Dictionary.

Answer: The Oracle Data Dictionary is a set of database tables and views that store metadata about the database’s structure and objects. It provides information about tables, columns, indexes, privileges, and other database-related details. It is a valuable resource for database administrators and developers.


35. How do you create a backup of an Oracle database using RMAN?

Answer: To create a backup of an Oracle database using RMAN, you can run the following command:

RMAN> BACKUP DATABASE;

This command backs up the entire database, including data files, control files, and archived redo logs.


36. What is the purpose of the Oracle SQL*Loader utility?

Answer: SQL*Loader is an Oracle utility used to load data from external files into database tables. It provides a fast and efficient way to import large volumes of data into an Oracle database.


37. Explain the concept of Oracle database tablespaces.

Answer: Oracle tablespaces are logical storage containers within a database. They group related database objects and data files together. Each tablespace can have one or more data files associated with it. Tablespaces are used to manage storage and allocate space for database objects.


38. How can you monitor and optimize SQL query performance in Oracle?

Answer: To monitor and optimize SQL query performance in Oracle, you can use tools like Oracle Enterprise Manager and Oracle Database Performance Analyzer. Additionally, you can use the EXPLAIN PLAN statement to analyze query execution plans and identify performance bottlenecks.

Example:

EXPLAIN PLAN FOR
SELECT * FROM your_table WHERE condition;

39. What is Oracle Real Application Clusters (RAC), and why is it used?

Answer: Oracle Real Application Clusters (RAC) is a feature that allows multiple Oracle database instances to run on separate servers while accessing a shared database. It provides high availability and scalability by distributing the workload across multiple nodes.


40. Explain the concept of Oracle flashback technology.

Answer: Oracle flashback technology allows you to view and recover data from a specific point in time without performing a database restore. It includes features like Flashback Query, Flashback Table, and Flashback Transaction to access historical data.


41. How can you grant and revoke privileges in Oracle?

Answer: To grant privileges in Oracle, you can use the GRANT statement. To revoke privileges, you can use the REVOKE statement. For example:

Granting a privilege:

GRANT SELECT ON your_table TO user;

Revoking a privilege:

REVOKE SELECT ON your_table FROM user;

42. Explain the purpose of the Oracle listener.ora and tnsnames.ora files.

Answer: The listener.ora file specifies configuration information for the Oracle listener. The tnsnames.ora file contains net service names, which are aliases for database connect descriptors. Both files are used to configure and manage database connections.


43. What is Oracle Transparent Data Encryption (TDE)?

Answer: Oracle Transparent Data Encryption (TDE) is a feature that encrypts data at the column, tablespace, or database level. It ensures that data is stored in an encrypted format on disk, providing enhanced security for sensitive information.


44. How do you create a new user in Oracle?

Answer: To create a new user in Oracle, you can use the CREATE USER statement. For example:

CREATE USER new_user IDENTIFIED BY password;

Replace new_user with the desired username and password with the user’s password.


45. Explain the concept of Oracle Data Guard.

Answer: Oracle Data Guard is a high-availability and disaster recovery solution for Oracle databases. It allows for the creation of standby databases that can take over in case of a primary database failure, ensuring data availability and protection.


46. How can you perform a full database export in Oracle using the Data Pump utility?

Answer: To perform a full database export using Oracle Data Pump, you can use the following command:

expdp SYSTEM/password FULL=Y DIRECTORY=your_directory DUMPFILE=full_export.dmp LOGFILE=full_export.log;

This command exports the entire database into a dump file.


47. What is the purpose of Oracle PL/SQL?

Answer: PL/SQL (Procedural Language/Structured Query Language) is Oracle’s extension of SQL that allows developers to write procedural code within the database. It is used for creating stored procedures, functions, and triggers to automate database tasks and enhance data manipulation capabilities.


48. How can you back up and restore the Oracle database control file?

Answer: You can back up the Oracle database control file using the ALTER DATABASE BACKUP CONTROLFILE TO TRACE statement. To restore it, you can use the SQL*Plus STARTUP command with the PFILE option and specify the control file trace as the parameter.


49. Explain the difference between a hot backup and a cold backup in Oracle.

Answer: A hot backup is taken while the database is running, and it involves backing up data files and archived redo logs. A cold backup is taken when the database is shut down, and it includes backing up all database files in a consistent state.


50. How can you enable and disable Oracle database options?

Answer: You can enable or disable Oracle database options using the DBMS_FEATURE_USAGE package. For example, to disable the partitioning option, you can run:

EXEC DBMS_FEATURE_USAGE.DISABLE ('Partitioning');

To enable an option, you can use ENABLE instead of DISABLE.


51. What is an Oracle trigger, and how is it used?

Answer: An Oracle trigger is a database object that automatically performs actions in response to specific events, such as INSERT, UPDATE, or DELETE operations on a table. Triggers are often used for enforcing data integrity rules, auditing changes, and automating tasks.

Example of creating a trigger:

CREATE OR REPLACE TRIGGER your_trigger
BEFORE INSERT ON your_table
FOR EACH ROW
BEGIN
  -- Trigger logic here
END;

52. Explain the purpose of the Oracle Materialized View.

Answer: An Oracle Materialized View is a database object that stores the result of a query as a precomputed table. It is used to improve query performance by allowing fast access to aggregated or precomputed data, reducing the need for complex joins or calculations.


53. What is Oracle Exadata, and why is it used?

Answer: Oracle Exadata is a database appliance designed for high-performance and scalability. It combines database servers and storage servers into a single, integrated platform. Exadata is used for processing large volumes of data quickly and efficiently, making it suitable for data warehouses and OLAP applications.


54. Explain the concept of Oracle flashback query.

Answer: Oracle flashback query allows you to query data as it existed at a specific point in time in the past. It is useful for retrieving historical data without the need for restoring the entire database.

Example:

SELECT * FROM your_table AS OF TIMESTAMP TO_TIMESTAMP('2022-01-01 08:00:00', 'YYYY-MM-DD HH24:MI:SS');

55. How can you monitor Oracle database performance?

Answer: You can monitor Oracle database performance using tools like Oracle Enterprise Manager, Oracle Performance Monitor (PerfMon), and Oracle Automatic Workload Repository (AWR). These tools provide insights into database activity, resource usage, and performance bottlenecks.


56. Explain the purpose of Oracle Database Auditing.

Answer: Oracle Database Auditing is a feature that allows you to track and log database activities, such as logins, SQL statements, and data access. It is used for security and compliance purposes, helping organizations detect and investigate suspicious or unauthorized database activity.


57. What is the role of an Oracle DBA (Database Administrator)?

Answer: An Oracle DBA is responsible for managing and maintaining Oracle databases. Their tasks include database installation, configuration, performance tuning, backup and recovery, security management, and ensuring data integrity and availability.


58. How do you perform database recovery in Oracle using RMAN?

Answer: To perform database recovery in Oracle using RMAN, you can use the RESTORE and RECOVER commands. For example:

RMAN> RESTORE DATABASE;
RMAN> RECOVER DATABASE;

These commands restore and recover the database to the specified point in time using backup files.


59. What is the purpose of Oracle Transparent Application Failover (TAF)?

Answer: Oracle Transparent Application Failover (TAF) is a feature that provides automatic reconnection and failover for database sessions in the event of a database or network failure. It ensures uninterrupted service for applications by redirecting sessions to a standby database.


60. Explain the concept of Oracle Data Pump.

Answer: Oracle Data Pump is a utility for importing and exporting database objects and data. It provides fast and efficient data movement between databases and is used for tasks such as backup and migration.

Example of exporting data:

expdp SYSTEM/password DIRECTORY=your_directory DUMPFILE=exported_data.dmp LOGFILE=export_log.log;

61. How can you identify and resolve locking issues in Oracle?

Answer: You can identify locking issues in Oracle by querying the DBA_BLOCKERS and DBA_WAITERS views to find blocking sessions. To resolve locking issues, you can either commit or roll back transactions in the blocking sessions or use tools like the Oracle Enterprise Manager to diagnose and address the problem.


62. What is Oracle GoldenGate, and why is it used?

Answer: Oracle GoldenGate is a data replication and integration tool used for real-time data movement and synchronization between heterogeneous databases. It is used for scenarios where high availability, data migration, and real-time data integration are critical.


63. How do you create and manage tablespaces in Oracle?

Answer: To create a tablespace in Oracle, you can use the CREATE TABLESPACE statement. For example:

CREATE TABLESPACE your_tablespace
DATAFILE 'your_datafile.dbf' SIZE 100M;

To manage tablespaces, you can use SQL statements like ALTER TABLESPACE to modify them and DROP TABLESPACE to remove them.


64. What is Oracle Database Vault, and what is its purpose?

Answer: Oracle Database Vault is a security feature that enhances database security by restricting access to specific data and database operations. It provides fine-grained control

over user privileges and helps prevent unauthorized access to sensitive data.


65. Explain the concept of Oracle Real Application Clusters (RAC).

Answer: Oracle Real Application Clusters (RAC) is a feature that allows multiple instances to access a single Oracle database simultaneously. It provides high availability and scalability by distributing database workloads across multiple servers, ensuring uninterrupted access to data.


66. What is the purpose of Oracle Data Guard?

Answer: Oracle Data Guard is a high-availability and disaster recovery solution that provides real-time data protection and synchronization between primary and standby databases. It ensures data availability and minimizes downtime in case of database failures.


67. Explain the difference between a primary key and a unique key constraint in Oracle.

Answer: Both primary key and unique key constraints enforce uniqueness in columns, but they have differences. A primary key constraint enforces uniqueness and ensures that the column(s) cannot contain null values, while a unique key constraint enforces uniqueness but allows null values.


68. What is the purpose of the Oracle Flashback Technology?

Answer: Oracle Flashback Technology provides features like Flashback Query, Flashback Table, and Flashback Database to recover lost data or reverse changes to a previous state. It is useful for data recovery and auditing purposes.


69. Explain the Oracle SQL*Loader utility.

Answer: Oracle SQL*Loader is a tool used for loading data from external files (such as CSV) into Oracle database tables. It provides flexibility and performance enhancements for bulk data loading tasks.

Example of loading data:

sqlldr username/password@service control=loader.ctl

70. What is an Oracle database link, and how is it used?

Answer: An Oracle database link is a database object that allows one database to connect and access objects in another database. It is used for distributed queries, sharing data between databases, and accessing remote database resources.

Example of creating a database link:

CREATE DATABASE LINK your_link
CONNECT TO remote_user IDENTIFIED BY remote_password
USING 'remote_db';

71. Explain the concept of Oracle PL/SQL.

Answer: Oracle PL/SQL (Procedural Language/Structured Query Language) is a programming language extension for SQL. It allows you to write procedural code, including loops, conditionals, and exception handling, within the Oracle database. PL/SQL is used for writing stored procedures, triggers, and functions.

Example of a PL/SQL procedure:

CREATE OR REPLACE PROCEDURE your_procedure AS
BEGIN
  -- Procedure logic here
END;

72. What is an Oracle database sequence, and how is it used?

Answer: An Oracle database sequence is an object that generates unique numeric values in an incremental or decremental order. It is often used for generating primary key values for tables.

Example of creating a sequence:

CREATE SEQUENCE your_sequence
START WITH 1
INCREMENT BY 1;

73. How can you improve the performance of Oracle SQL queries?

Answer: To improve Oracle SQL query performance, you can:

  • Use proper indexing on columns frequently used in WHERE clauses.
  • Optimize SQL statements by avoiding unnecessary joins or subqueries.
  • Monitor and analyze query execution plans.
  • Use bind variables instead of literals to reduce parsing overhead.
  • Implement partitioning for large tables.
  • Use materialized views for frequently used queries.

74. Explain the concept of Oracle Automatic Storage Management (ASM).

Answer: Oracle Automatic Storage Management (ASM) is a storage management solution that simplifies database storage administration. It provides features like automatic disk rebalancing, mirroring, and striping to optimize storage performance and reliability.


75. How do you perform a backup and recovery in Oracle using RMAN (Recovery Manager)?

Answer: To perform backup and recovery in Oracle using RMAN, you can use commands like BACKUP DATABASE to create backups and RECOVER DATABASE to restore and recover the database to a specific point in time.

Example of backup:

RMAN> BACKUP DATABASE PLUS ARCHIVELOG;

Example of recovery:

RMAN> RECOVER DATABASE UNTIL TIME 'YYYY-MM-DD HH:MI:SS';

76. What is Oracle Database In-Memory, and why is it used?

Answer: Oracle Database In-Memory is a feature that allows you to store and query data in-memory for improved performance. It is used for accelerating analytics and reporting queries by reducing disk I/O and providing faster query response times.


77. Explain the purpose of Oracle SQL Plan Baselines.

Answer: Oracle SQL Plan Baselines are used to capture and preserve efficient execution plans for SQL statements. They help ensure consistent query performance by preventing the optimizer from choosing suboptimal execution plans.


78. What is Oracle Cloud Infrastructure (OCI), and how does it relate to Oracle databases?

Answer: Oracle Cloud Infrastructure (OCI) is Oracle’s cloud computing platform. It provides a range of services, including Infrastructure as a Service (IaaS) and Platform as a Service (PaaS). OCI offers Oracle Database Cloud Service, which allows users to deploy and manage Oracle databases in the cloud

.

Example of launching an Oracle database in OCI:

oci db autonomous-database create --db-name your_db --cpu-core-count 2 --data-storage-size-in-tbs 10 --admin-password your_password

79. Explain the concept of Oracle Edition-Based Redefinition.

Answer: Oracle Edition-Based Redefinition (EBR) is a feature that allows multiple versions of PL/SQL objects (such as procedures and functions) to coexist in the same database schema. It is useful for making changes to database objects without impacting existing applications.

Example of creating a new edition and switching:

CREATE EDITION new_edition;
ALTER SESSION SET EDITION = new_edition;

80. What is Oracle Transparent Data Encryption (TDE), and why is it used?

Answer: Oracle Transparent Data Encryption (TDE) is used to encrypt sensitive data stored in database columns, tablespaces, or backups. It ensures that data remains confidential even if the physical storage media is compromised. TDE is essential for data security and compliance.

Example of enabling TDE:

ALTER TABLESPACE your_tablespace ENCRYPT;

81. What is Oracle Real Application Clusters (RAC), and why is it used?

Answer: Oracle Real Application Clusters (RAC) is a database clustering solution that allows multiple Oracle database instances to run on a cluster of interconnected servers. It is used to provide high availability and scalability for Oracle databases by distributing the workload across multiple nodes.


82. Explain the purpose of Oracle Data Pump.

Answer: Oracle Data Pump is a utility used for importing and exporting database objects and data. It provides efficient mechanisms for moving data between Oracle databases and is commonly used for backups, data migration, and data provisioning.

Example of exporting data:

expdp username/password@service DIRECTORY=your_dir DUMPFILE=your_dumpfile.dmp

83. What is Oracle GoldenGate, and how does it work?

Answer: Oracle GoldenGate is a data replication and integration solution used for real-time data movement and synchronization between heterogeneous systems. It captures and delivers changes from source to target systems, ensuring data consistency and availability across the enterprise.


84. Explain the use of Oracle Exadata.

Answer: Oracle Exadata is an engineered system designed for high-performance data warehousing and OLTP workloads. It combines database servers, storage servers, and optimized software to deliver exceptional database performance and scalability.


85. What is Oracle Database Vault, and why is it used?

Answer: Oracle Database Vault is a security feature that restricts access to sensitive data and database configurations. It is used to enhance database security by enforcing separation of duties and limiting privileged access to authorized users.

Example of enabling Oracle Database Vault:

ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;

86. Explain the concept of Oracle Cloud Autonomous Database.

Answer: Oracle Cloud Autonomous Database is a fully managed database service in Oracle Cloud Infrastructure (OCI). It automates database administration tasks, including patching, tuning, and backups, allowing users to focus on application development rather than database management.

Example of creating an Autonomous Database:

oci db autonomous-database create --db-name your_db --cpu-core-count 2 --data-storage-size-in-tbs 10 --admin-password your_password

87. How do you monitor and optimize Oracle database performance?

Answer: Monitoring and optimizing Oracle database performance involves:

  1. Using tools like Oracle Enterprise Manager (OEM) for performance monitoring.
  2. Analyzing SQL execution plans and optimizing queries.
  3. Tuning database parameters for optimal resource allocation.
  4. Properly indexing tables and maintaining statistics.
  5. Implementing partitioning and compression for large tables.
  6. Using AWR (Automatic Workload Repository) reports for performance analysis.

88. What is Oracle NoSQL Database, and when is it preferred over relational databases?

Answer: Oracle NoSQL Database is a distributed, highly available, and scalable database designed for handling large volumes of unstructured or semi-structured data. It is preferred over relational databases for use cases such as IoT data, social media data, and real-time analytics where data is rapidly changing and doesn’t fit well into traditional tabular structures.


89. Explain the purpose of Oracle Advanced Queuing (AQ).

Answer: Oracle Advanced Queuing (AQ) is a messaging system used for asynchronous communication between different components of an application or between applications. It provides a reliable message queuing mechanism for decoupling producers and consumers of messages, ensuring message delivery and processing.

Example of creating an AQ queue:

DBMS_AQADM.CREATE_QUEUE_TABLE(queue_table => 'your_queue_table', queue_payload_type => 'SYS.AQ$_JMS_TEXT_MESSAGE', storage_clause => 'PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255', queue_type => sys.dbms_aqadm.default_queue_type, comment => 'Your queue comment');

90. How does Oracle handle transaction management and ACID properties?

Answer: Oracle uses a combination of features like transactions, locks, and the REDO log to ensure ACID (Atomicity, Consistency, Isolation, Durability) properties. Transactions are managed using COMMIT and ROLLBACK statements to control changes to the database. REDO logs are used for recovery, ensuring that committed changes are durable even in case of a system crash.


91. Explain the purpose of Oracle Flashback Query.

Answer: Oracle Flashback Query allows users to view the data as it existed at a specific point in time in the past. It’s useful for auditing, historical analysis, and debugging by querying past versions of rows in a table.

Example of using Flashback Query:

SELECT * FROM your_table AS OF TIMESTAMP TO_TIMESTAMP('2023-01-01 12:00:00', 'YYYY-MM-DD HH24:MI:SS');

92. What is an Oracle Materialized View, and when would you use it?

Answer: An Oracle Materialized View is a database object that stores the result of a query in a physical table. It is used to improve query performance by precomputing and storing the result set. Materialized views are commonly used in data warehousing and reporting scenarios.

Example of creating a Materialized View:

CREATE MATERIALIZED VIEW your_mv AS SELECT * FROM your_table;

93. Explain the concept of Oracle Database Sharding.

Answer: Oracle Database Sharding is a database architecture that horizontally partitions data across multiple databases or shards. It’s used for scalability and high availability. Each shard stores a subset of data, and a coordinator database manages data distribution and routing.

Example of enabling sharding:

ALTER DATABASE SHARD your_shard ADD TABLESPACE your_tablespace;

94. What is Oracle Transparent Data Encryption (TDE), and why is it used?

Answer: Oracle Transparent Data Encryption (TDE) is a security feature used to encrypt sensitive data at the column, table, or tablespace level. It’s used to protect data at rest to prevent unauthorized access to sensitive information.

Example of enabling TDE on a tablespace:

ALTER TABLESPACE your_tablespace ENCRYPTION ONLINE ENCRYPT USING 'AES256' NO SALT;

95. How do you perform a backup and recovery in Oracle?

Answer: Oracle backup and recovery involve several steps:

  1. Backup: Use RMAN (Recovery Manager) for full database backups.
  2. Archive Logs: Regularly back up archive logs for point-in-time recovery.
  3. Recovery: In case of data loss, restore the database using backups and apply archived logs.
  4. Data Pump: Import data from backups if necessary.

Example of RMAN backup:

RMAN> BACKUP DATABASE PLUS ARCHIVELOG;

96. Explain the Oracle Database Auditing feature.

Answer: Oracle Database Auditing is used to monitor and record user actions within the database. It can track SQL statements, access to specific objects, and system-level activities. Auditing helps in security, compliance, and troubleshooting.

Example of enabling database auditing:

AUDIT SELECT TABLE BY your_user;

97. What is Oracle Data Guard, and why is it used?

Answer: Oracle Data Guard is a high-availability and disaster recovery solution that provides standby databases for automatic failover and data protection. It’s used to ensure data availability and minimize downtime in case of system failures.

Example of creating a physical standby database:

CREATE STANDBY DATABASE;

98. Explain the purpose of Oracle Advanced Security.

Answer: Oracle Advanced Security is used to enhance database security by providing features like network encryption, data encryption, and strong authentication. It ensures that data is secure during transmission and storage.

Example of enabling network encryption:

SQLNET.ENCRYPTION_SERVER = REQUIRED
SQLNET.ENCRYPTION_TYPES_SERVER = (AES256)

99. How does Oracle handle data concurrency and locking?

Answer: Oracle uses locks to manage data concurrency. Locks prevent multiple transactions from modifying the same data simultaneously, ensuring data integrity. Oracle supports various types of locks, such as row-level locks and table-level locks, to handle concurrency.

Example of locking a row:

SELECT * FROM your_table WHERE column_name FOR UPDATE;

100. Explain the purpose of Oracle Data Redaction.

Answer: Oracle Data Redaction is a security feature that dynamically masks sensitive data in query results. It’s used to protect confidential information from unauthorized users while allowing legitimate users to access the data.

Example of enabling data redaction:

DBMS_REDACT.ADD_POLICY('your_table', 'column_name', 'FULL', 'DBMS_REDACT.FULL', '1=1', 'REDACT');