Oracle DBA Interview Questions

1. What Is Oracle Database?

Ans: Oracle Database is an extensive and advanced relational database management system (RDBMS) designed to handle vast data storage and retrieval efficiently. It separates itself by dividing physical and logical structures, allowing for flexible data management and optimized access.

2. Differentiate between Oracle DBA and Oracle Developer

Ans:  

Oracle DBA: Focuses primarily on database management, overseeing streamlined tasks, including maintenance, backup, recovery, and server connectivity. Operates chiefly in backend database management.

• Oracle Developer: Concentrates on front-end development, involving a broader spectrum of responsibilities such as coding, UI design, and database development.

3. You want to find out how many users are defined in the password file and what privileges those users have. How would you accomplish this?

Ans: Utilize the “v$pwfile_users” view in SQL. By executing SELECT * FROM v$pwfile_users;, you can access detailed information about each user's privileges in the password file, including USERNAME, SYSDBA, SYSOPER, and SYSASM Privileges.

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4. What are the roles of DBA?

Ans: A DBA plays a crucial role in database management, responsible for user administration, storage management, security, performance monitoring, and executing backup and recovery protocols.

5. What are the common Oracle DBA tasks?

Ans: The most common tasks of an Oracle DBA include Oracle software installation, database creation and upgrading, performance tracking, storage management, user & security management, etc. Further, it also ensures solid backup and recovery processes.

6. Name the various Oracle database objects.

Ans: Key objects in Oracle databases include Sequences, Views, Tables, Tablespaces, and Indexes.

7. What are the contents of the control file?

Ans: A control file is vital for an Oracle database, containing essential information like the database name, datafile and redo log file locations, database creation timestamp, log sequence number, and checkpoint details.

8. What Is A Tablespace?

Ans: A Tablespace in Oracle is used for logical data storage, consisting of one or more data files, and can contain objects from different schemas.

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9. How are indexes updated within the Oracle Database?

Ans: Any changes in the index will automatically be updated by Oracle as it uses and maintains the indexes. Further, Oracle will automatically distribute the changes made within the table data into the applicable indexes.

10. What Is A Segment?

Ans: A Segment in Oracle is a set of extents allocated for specific data structures and stored in the same tablespace.

11. What Is An Index?

Ans: An Index in Oracle is a structure linked to tables or clusters, enhancing SQL statement execution speed by providing a faster access path to table data.

12. List out the tools for administering the database.

Ans: Tools for database administration include the following:

• Oracle Universal Installer
• Database Configuration Assistant
• Database Upgrade Assistant
• Oracle Net Manager
• Oracle Enterprise Manager.

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13. What are the dictionary tables used to monitor a database space?

Ans: Dictionary tables like DBA_FREE_SPACE, DBA_SEGMENTS, and DBA_DATA_FILES are instrumental in monitoring database space.

14. What are the differences between EBU and RMAN?

Ans: EBU (Enterprise Backup Utility) is used for backing up Oracle7 databases. At the same time, RMAN (Recovery Manager) is a more advanced utility introduced in Oracle8 and above, offering enhanced features with no direct upgrade path from EBU.

15. What is the logical structure of the disk resources?

Ans: Oracle's logical disk structure encompasses Data Blocks, Extents, Tablespaces, and Segments, each serving a specific data organization and storage function.

16. What different stages will an Instance pass while starting a database?

Ans: An Oracle database instance transitions through:

• NoMount Stage.
• Mount Stage.
• Open Stage, where the database becomes accessible to users.

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17. What are the different levels of auditing?

Ans: Auditing in Oracle can be categorized into Statement Auditing, Privilege Auditing, and Object Auditing, each tracking different aspects of database usage and access.

18. Why is performance tuning a menacing area for DBAs?

Ans: Performance tuning requires a blend of technical expertise and analytical skills, as it involves diagnosing and resolving issues related to process inefficiencies and application scalability.

19. What are the dynamic performance views? Who has access to these views?

Ans: Dynamic performance views, also known as V$ views, provide session information. Access is typically granted through the SELECT_CATALOG_ROLE role, available to any Oracle user.

20. What is an ASM instance?

Ans: An ASM (Automatic Storage Management) instance manages disk groups comprising the System's Global Area (SGA) and background processes, essential for efficient database file layout and metadata management.

21. What Is A Synonym?

Ans: A Synonym in Oracle provides an alternative name for another database object, offering abstraction and protecting applications from changes in base object definitions.

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22. What is an ASM Disk Group?

Ans: ASM Disk Groups are clusters of disks managed by ASM, simplifying database storage and reducing I/O overhead.

23. Which components of your database environment can be protected by an “Oracle Restart” configuration?

Ans: Oracle Restart safeguards Database Instances, ASM, Oracle NET Listener, ASM Disk Groups, Database Services, and Oracle Notification Services.

24. Which tools can you use to start up an Oracle database?

Ans: Tools for database startup include SQL*Plus, Oracle Enterprise Manager, and RMAN.

25. What is Data Normalisation?

Ans: Data Normalization is reorganizing data in the database to ensure clean, structured, and redundant-free data, facilitating efficient analysis and querying.

Oracle DBA Interview Questions and Answers for Experienced

26. Explain the procedure of restoring RMAN for the recovery if all the instances are down.

Ans: Restoring RMAN involves:

• Shutting down all nodes.
• Starting a node to convert data files and archive logs.
• Recovering the node.
• Opening the database.
• Bringing other nodes up.
• Confirming operational status.

27. Explain Briefly Shared Server Architecture.

Ans: Shared Server Architecture in Oracle reduces the need for dedicated server processes by routing requests to a shared pool of server processes, optimizing memory use and user support.

28. Which files must be backed up?

Ans: Essential files for backup include Database files, Control files, Archived log files, Password files, and INIT.ORA.

29. What Is Rollback Segment?

Ans: A Rollback Segment in a database facilitates transaction rollbacks and data recovery.

30. What is a backup set?

Ans: A backup set in the RMAN context is a collection of backup files generated by an RMAN backup command consisting of one or more backup pieces.

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31. What are the architectural components of RMAN?

Ans: RMAN architecture comprises the RMAN executable, server processes, channels, target database, recovery catalog database, media management layer, and backups.

32. What does RMAN backup consist of?

Ans: An RMAN backup includes a backup of part or all of a database, resulting from an RMAN backup command, and comprises one or more backup sets.

33. What do you mean by recovery catalog?

Ans: A recovery catalog is a repository of metadata used by RMAN for restoration and recovery processes. It stores detailed information about data files, backup history, archived redo logs, and more.

34. What are the uses of a database Resource Manager?

Ans: The database Resource Manager limits idle session duration, terminates long-running SQL statements, sets initial login priorities for consumer groups, and specifies the maximum number of active sessions for a consumer group.

35. What is a Resource Plan?

Ans: A Resource Plan dictates how resources are allocated among various consumer groups, specifying the percentage of resources like CPU time each group receives.

36. What are the main aspects of Oracle Database Security Management?

Ans: Key aspects include:

• Controlling data access.
• Restricting access to legitimate users.
• Ensuring accountability.
• Safeguarding critical data.
• Managing overall enterprise security.

37. How does the process of Database Writer work in Oracle?

Ans: Oracle’s Database Writer, or DBWn, is integral to its architecture. It transfers 'dirty' buffers from the database buffer cache to disk. This process is crucial when a server updates a data block, which is read into the cache and marked as 'dirty' for subsequent writing to disk if not found in the buffer cache.

38. List the instance parameters used to configure “Shared Server Architecture”?

Ans:

• SHARED_SERVERS
• CIRCUITS
• MAX SHARED_SERVERS
• DISPATCHERS
• SHARED_SERVER SESSIONS

39. How do you find the total database size in the database?

Ans: The database size can be determined using views such as dba_segments for used space, dba_data_files for datafile space, and v$log for redo log file information.

40. How can you improve the performance of Sql*loader?

Ans: Performance can be improved by using direct path load and removing indexes and constraints during load operations.

41. What are the responsibilities of the Database Admin’s tasks?

Ans: A DBA's responsibilities include:

• Installing and upgrading Oracle tools.
• Allocating system storage.
• Creating database structures.
• Managing user access and security.
• Performance optimization.
• Backup and recovery.
• Technical support coordination.

42. Do we use the Materialised View?

Ans: Materialized views, also known as summaries, are used to store and compute aggregated data, such as sales figures.  These are crucial in decision-making processes within data centres.

43. How do you create a SYSTEM Tablespace in Oracle?

Ans: Every database within Oracle contains a tablespace named “SYSTEM”. At the time of database creation, this tablespace is automatically created. Also, it includes a data dictionary table for the entire data.

44. Explain Oracle Grid Architecture.

45. How Oracle Works?

Ans: Oracle operates by starting an instance, establishing client-server connections, executing SQL statements, managing data in the SGA, and maintaining a robust transaction and recovery system.

46. What are the Data Files properties?

Ans: A data file is unique to a database, with a fixed size post-creation, and links to only one database at a time.

47. Define Redo Log Files.

Ans: Redo log files are crucial for database recovery, recording all modifications to facilitate restoration in case of data corruption or loss.

48. What Is An Extent?

Ans: An Extent in Oracle DB is a set of contiguous Oracle data blocks, forming part of a segment and assigned to store specific information.

49. Define the various types of Synonyms.

Ans: Oracle Database utilizes two synonym types:

• Public Synonyms: Accessible by all database users, independent of schema.
• Private Synonyms: Restricted to the creator within a specific schema.

50. What Is The Difference Between Large Dedicated Server And Oracle Grid?

Ans: Costly components and high incremental costs characterize large dedicated servers, while Oracle Grid utilizes low-cost modular components, low total costs, and provides enterprise services at a lower price.

51. What is meant by Data Files?

Ans: Data files in Oracle are key components storing database data. They are constituted as physical files within the OS. Further, they are uniquely identified and developed for each tablespace.

52. Name the keyword useful to get distinct records from a table in the Oracle database.

Ans: The 'SELECT DISTINCT' keyword retrieves unique records from a table.

53. How do you define - Table Dropping, Table Truncating, & Deleting Records within a Database table?

Ans:

• Dropping a Table: Removes both the table and its indexes.
• Truncating a Table: Empties the table by removing all records without logging the individual row deletions.
• Deleting Records: Removes records while maintaining transaction log details.

54. Define the various types of Segments.

Ans: Oracle database segments include:

• Index Segment.
• Temporary Segment.
• Rollback Segment.
• Data Segment.

55. What Is A Control File?

Ans: A Control File is a binary file storing crucial database information such as the database name, data files, redo files, creation time, and log sequence number.

56. What is the definition of GROUP BY?

Ans: The GROUP BY clause in Oracle is used to collect data from different records and group them, with each group having distinct row values for the specified columns.

57. The main function(s) of the redo log is?

Ans: The primary function of the redo log is to record all database modifications, enabling the reconstruction of changes and securing rollback data.

58. What Are The Computing Components Of Oracle Grid?

Ans: Oracle Grid computing components include Oracle Enterprise Manager and Grid Control, Oracle 10g Database with Real Application Clusters, and ASM Storage Grid.

59. What Is the Recoverer Process?

Ans: The Recoverer process (RECO) in a distributed database configuration automatically resolves failures in distributed transactions.

60. What Are Job Queue Processes?

Ans: Job Queue Processes in Oracle Database automate the execution of PL/SQL processes using background processes and catalog tables.

61. Define SQL*Plus.

Ans: SQL*Plus is Oracle database’s freely distributed command-line tool. Using SQL*Plus, you can interactively submit various SQL queries to the server. 

Oracle DBA Interview Questions and Answers - Advanced

62. What Are Archiver Processes?

Ans: Archiver Processes copy redo log files to storage devices post-log switch, functioning only in ARCHIVELOG mode with automatic archiving enabled.

63. What Is Server Virtualization?

Ans: Server Virtualization in Oracle RAC enables a single database to operate across multiple clustered nodes, pooling processing resources.

64. What Is Storage Virtualization?

Ans: Oracle ASM provides storage virtualization, creating a virtual layer between the database and storage for efficient disk group management.

65. What Is a Grid Management Feature?

Ans: Oracle Enterprise Manager 10g's Grid Management feature allows managing multiple systems as a logical group through a single console.

66. What Are Data Blocks?

Ans: Oracle stores data in Data Blocks, specific byte-sized spaces on disk, serving as the minor logical storage units.

67. When Oracle Allocates An SGA?

Ans: After reading initialization parameters to determine values, Oracle allocates an SGA (System Global Area) during startup.

68. What Is An Oracle Instance?

Ans: An Oracle Instance comprises the SGA and Oracle processes, coming into existence when the database is started.

69. What Are The Several Tools For Interacting With The Oracle Database Using Sql?

Ans: Tools include Oracle SQLPlus and iSQLPlus, Oracle Forms, Reports, Discoverer, Oracle Enterprise Manager, and third-party tools.

70. How Views Are Used?

Ans: Views in Oracle provide security by restricting access, hiding data complexity, simplifying user queries, and presenting data from a different perspective.

71. What Contains Oracle Physical Database Structure?

Ans: The physical structure includes data files, Control Files, Redo Log Files, Archive Log Files, Parameter Files, Alert and Trace Log Files, and Backup Files.

72. What Is A Dimension?

Ans: A Dimension in Oracle represents hierarchical relationships between column pairs or column sets, tying child and parent values.

73. Explain Sequence Generator In Oracle.

Ans: Oracle's sequence generator provides a sequential series of numbers for generating unique sequential numbers independent of any tables.

74. What is the definition of the transaction?

Ans: A Transaction in Oracle is a series of SQL statements treated as a single unit, uniquely identified and adhering to ACID properties, encompassing bill pay and purchasing operations.

75. What is the definition of SQL?

Ans: SQL is a popular language for managing and operating data within the RDBMS. There is a great scope of SQL that includes query, input data, delete and update, data access control, etc.

76. What do you understand about the public database link?

Ans: A Public database link in Oracle provides a shared access path to a remote Oracle Database, available to all users.

77. What are the benefits of ORDBMS?

Ans: ORDBMS offers benefits like storing complex data types, integrating object-oriented programming languages, SQL query capabilities, and ease of learning.

78. In order to get total records from a table, what is the keyword?

Ans: The COUNT keyword retrieves the total number of records in a table, including counting NULL values with COUNT(*).

79. What is the use of the SELECT statement?

Ans: The “SELECT” statement recovers data from database tables, views, or materialized views based on specified SQL query instructions.

80. Define Sequence

Ans: A Sequence is a database object and it produces a series of numeric values, mainly used to produce unique table values.

81. How do you switch from an init.ora file to a spfile?

Ans: To switch from an init.ora file to a spfile, you need to create a spfile from the pfile command and restart the instance using the spfile.

82. What types of backups are there in Oracle?

Ans: Oracle databases uses four types of primary backups:

• Cold Backup: This includes backing up data when the database is offline.
• Import/Export Backup: Uses Oracle's import/export functionality for data backup.
• Hot Backup: It is executed when the database is active and ongoing.
• RMAN Backup:  It relies on Oracle's Recovery Manager for a more detailed backup solution.

83. Difference between a Grid and a Cluster.

Ans:

• Cluster: Utilized in grid infrastructure creation, it consolidates resources for specific applications, commonly employed in database and web logic app servers.
• Grid: This represents a more extensive network comprising multiple clusters, sharing resources across diverse apps and users. It's characterized by its versatility in managing different types of applications across servers.

84. What type of information is required when you create a Sequence?

Ans: Creating an Oracle sequence involves specifying:

• A unique name for the series.
• The starting number.
• Incremental values.
• The 'no cycle' attribute ensures the line resets after completion.
• 'No cache' setting, determining the caching of sequence numbers.

85. Name the different types of Disc components of Oracle.

Ans: Key physical components of an Oracle database include:

• Redo Log Files.
• Password Files.
• Control Files.
• Data Files.
• Parameter Files.

86. How can you start your database automatically after rebooting the server?

Ans: To automate database startup post-server reboot:

• Oracle Restart:- A feature of Oracle High Availability Service requiring Grid Infrastructure.
• Custom Script:- Writing and implementing a startup script in the OS.

87. Name the various types of SQL Statements

Ans: Oracle SQL includes:

• • Data Manipulation Language (DML).
  • Data Definition Language (DDL).
  • Session & System Control.
  • Transaction Control.

88. What keyword is used to get sorted records from the table?

Ans: The keyword 'ORDER BY' is used to sort records in a table.

89. Define Parameter File.

Ans: A parameter file is a configuration file containing various initialization parameters and their values, essential for database operation.

90. Define the way to find the Oracle Database Version

Ans: To identify the Oracle Database version, you need to run the query 'SELECT * FROM V$VERSION' in the command prompt. It will fetch the version details from the v$version table.

91. How would you develop a Response File to speed up database installations?

Ans: Response files, used for streamlined database installations, are created by customizing a template or using the Oracle Universal Installer in record mode. It will automatically document the installation steps.

92. What are the roles and responsibilities of Oracle DBAs?

Ans: Below is the list of roles and duties of any Oracle DBA;

• Helps to assess the database performance and implement security measures for any information system.
• Helps to develop information security policies and procedures.
• Update any database information and create the database table to store the datasets.
• Helps to set up the database parameters and specifications.
• Developing performance-related metrics and standard information technologies.

93. What do you know about the Oracle database?

Ans: Oracle data base is one of the multi-model database management tools; this tool is developed and marketed by Oracle corporations. The main purpose of using the Oracle database tool is to run any online transaction processing, data warehousing, and work well with mixed database workloads.