Top 25 Oracle DBA Interview Questions and Answers in 2022

Oracle Database Administrators (DBAs) use Oracle’s database software solutions to manage and store data. Businesses and enterprises trust Oracle database administrators to manage their data securely and efficiently. DBAs oversee all elements of an Oracle database, including installation, setup, design, data migration, and database server hardware evaluation. Additional roles include data recovery, security, backups, and performance monitoring.

We’ll discuss the most relevant and critical interview questions as you begin your database administrator or DBA path in this article. Although work learning is an ongoing process, some particular skills and concepts must be mastered straight away.  In my opinion, DBAs should obtain a thorough understanding of how their databases interact with various components such as the operating system, network, firewalls, server hardware, and storage systems, to name a few. This concept will serve as the foundation for my recommendations.

1. Briefly Describe Oracle.

Oracle is both a company and a database server, managing data in a well-organized manner. In a multi-user context, it enables users to save and retrieve related data so that multiple users can access the same data simultaneously, delivering excellent performance while accomplishing all of this. A database server also offers solutions for failure recovery and prevents illegal access. A backup of a primary database is used to construct a database replica, known as a standby database.

2. How Do Oracle Databases Work?

Oracle offers software for setting up and maintaining the Oracle Database. The system, user, and control information are stored in the database’s logical and physical structures. The Oracle Database Server controls the database. The Oracle Database System refers to both the actual database and the software that operates it.

The data is kept in memory using a database buffer cache for faster access. All database changes are recorded and kept in the redo logs. A control file keeps track of the physical layout of the database, while a Data Guard assures data security and high availability.

3. What Is The Purpose Of The Password File?

The database’s data dictionary contains user passwords. When a user attempts to log into the database, the values in the database are compared to the user’s usernames and passwords. Only if the username and password match does the user gain database access. The data dictionary is kept in the database and can be accessed as long as the database is up and running. The dictionary also contains the administrators’ passwords.

It wouldn’t be possible to access the data dictionary until the database is locked.  Restarting a crashed database is one of the administrator’s duties. There must be a way for them to log in even if the database is locked. The password file is useful in this situation. A password file is an operating system file kept separate from the database on a different disc. For users with SYSDBA or SYSOPER access, it keeps their username and password. When the database is unavailable, administrators with specific privileges are authenticated using password files.

4. How Do Data Files Work?

Data files house all of the tables. Each piece of data is stored in a data file. The database data is stored in the data files. The database’s data files are where relational database structures’ data, such as tables and indexes, are physically kept.

5. What Does Oracle’s Grid Architecture Entail?

For business computing, Oracle’s grid design combines a sizable database server, memory, and connectivity to produce a tailored, as-needed computing resource. The grid computing architecture continuously assesses resource consumption and modifies supply as necessary.

A grid of various connected database servers, for instance, might be used to run multiple programs simultaneously. The database administrator might automatically assign a dedicated server to that program to handle the escalating demands if monthly reports are overdue.

Advanced workload management techniques in grid computing allow programs to collaborate across multiple servers. Resources within a region can be offered dynamically, and data processing capacity can be increased or eliminated as needed. Web services make it possible to quickly integrate apps to start a business.

6. What Distinguishes An Oracle DBA Role From An Oracle Developer Role In A Company? Do These Also Resemble One Other In Any Way?

Backend application development is primarily the responsibility of an Oracle developer. They produce restrictions such as tables and indexes. They must also be knowledgeable in PL/SQL and SQL because processes are created using these languages. On the other hand, managing the database software is not necessary for Oracle engineers.

However, managing the database, which includes tasks like maintenance to keep the databases operating, creating backups, upholding privacy rules, and other things, is the duty of an Oracle DBA. Code authoring is not frequently assigned to DBAs. As they are also crucial for database administration, DBAs need to have a solid understanding of SQL and PL/SQL, just like developers do. Depending on the organizational structure, DBAs may be given development-related duties or, at the very least, assist developers when necessary.

7. Which Skills Are Essential For An Oracle DBA?

For a DBA, communication is a necessary skill. A DBA must be able to interact not only with business stakeholders but also with other members of the IT team. Problem-solving abilities are also crucial since there will always be problems that need to be solved. Time management is another essential ability because it enables me to prioritize my duties to meet deadlines.

8. What Steps Would You Take To Fix A Database Problem?

I would start by identifying the problem’s root cause by examining its symptoms. After that, I would look for any errors in the logs or warnings pointing to a potential issue. I would then execute diagnostic queries to determine the issue’s primary cause. If it’s a problem with the application, I’ll contact the creator for more help. I’ll try restarting the server and rerunning the query if it’s a database problem. If the problem still occurs, I’ll examine the network connection and make sure the user has access rights to the database.

9. What Data Migrating Experience Do You Have?

In my previous position, I was responsible for transferring data from our current system to a new cloud-based system. To avoid problems once the new system was operational, the company intended to transfer all of its data to it before the new system went live. I had to ensure that every piece of data was transferred. This project took me several months to finish.

10. Give An Instance Where You Exhibited Technical Leadership.

In my previous position as an Oracle DBA, I was the only person in the IT division who understood how to use Oracle Enterprise Manager. The business brought on a new developer who required access to the database but had no prior experience with it. I spent some time guiding him through the program’s interface and offering him pointers for making better use of it. He valued the assistance and picked things up quickly.

11. If You Saw That Database Performance Was Beginning To Deteriorate, What Would You Do?

I would check the system resources first to see if there were any problems with CPU or memory utilization if I saw that database performance was starting to deteriorate. If there were no issues with these resources, I would look for network and storage system constraints. To identify which processes are causing issues, I would examine the database’s wait events and latch contention reports if I was still unable to locate the problem.

12. What Exactly Does “Recovery Catalog” Mean?

The metadata that RMAN manages for data restoration and recovery procedures is found in a database structure called the recovery catalog. A recovery catalog houses the metadata that RMAN uses for the reinstallation and recovery processes. Even if the target control file and all backups are deleted, the RMAN metadata is still available in the recovery catalog.

13. Describe The Specifics Of The Deadlock.

When two operations attempt to modify rows in a table constrained by a third operation, deadlock results. This typically results from insufficient row lock requests being made. The server’s productivity will deteriorate due to this circumstance, which might be due to an application with a poor UI design. These constraints will be instantly released when a commit or rollback action is performed or when any of these processes are halted.

14. What Exactly Is A Scope Parameter?

When using a file, a variety of parameters can be updated flexibly. The benefit of spfile over file is that there are three possible scope values for each value you can modify while the database is running: file, memory, and occasionally both. After the subsequent reboot, the scope of the spfile will change, the storage range will change promptly but roll back, and both will change swiftly.

15. What Tools Could You Use To Launch An Oracle Database?

Three tools are available for starting a database:

  • SQL *Plus: The startup SQL *Plus command can be used to start an Oracle database instance.
  • Oracle Enterprise Manager is a system administration utility that enables you to launch the Oracle database. It offers a comprehensive approach to managing your diverse environment. You can still sign in to OEM if the database is stopped. By determining that the database is down, it will show you the “Start” button.
  • Recovery Manager: RMAN refers to the RMAN repository associated with the TARGET keyword, which is also a database on which RMAN executes backup and recovery operations in the database’s control file.

16. How Does The “Database Writer” Process Work?

It is feasible to run multiple database context processes. The operating system refers to them as “down.” This process is responsible for keeping “dirty” buffers on the hard drive. If a data block needs to be updated, a server process reads it from the disc into the buffer cache, changes the cache copy, and then reads the block from the disc if it isn’t already there. Therefore, an updated database block in the buffer cache is called a “dirty” block.

17. Why Does Performance Tuning Provide A Concern To DBAs?

According to me, the performance tuning field cannot be automated like other exp/imp aspects like backup recovery. Application programmers and DBAs need to do more research in this area to figure out why some processes are taking longer than they should, why we can’t extend apps to more users without experiencing performance deterioration, etc. Our technical expertise is useful in this area, coupled with ongoing experimentation and observation.

18. What Exactly Is An ASM Instance?

ASM disk groups are managed by this instance. It consists of background processes and the system’s global area (SGA). A disk group that is made available to the database instance is mounted by an ASM instance. The database instances receive file layout details from an ASM instance, which controls a disk group’s metadata.

19. How Do Archiver Processes Work?

Following a log switch, it moves and redoes log files to a specific storage location. The archiver processes are present when the database is in ARCHIVELOG mode and automatic archiving is enabled. There are ten architectural processes per Oracle instance (ARC0 to ARC9). When there are not enough archivist processes to manage the workload, the LGWR process initiates a new ARCA process.

20. Do You Have Any Previous Working Expertise Of Huge Database Systems?

In my previous position, I was in charge of maintaining a 100+ GB enterprise-level Oracle database system. The company kept customer data, financial records, and other essential documents in this database system. To avoid complications, my team and I had to make sure we continuously watched the system. We also wanted to ensure that backups were regularly done.

21. What Exactly Is A Tablespace?

Oracle uses tablespace to store logical data. Data will be physically saved in data files. The tablespace will be linked to data files. There can be several data files in a tablespace. A tablespace can include items from various schemas, and a schema can contain many tablespaces. During database construction, the “SYSTEM tablespace” is created by default. It contains read-only data dictionary tables containing database information.

22. What Actions Do You Take To Guarantee A Smooth Transition While Implementing System Upgrades?

In my previous position, I was in charge of updating our database server from Oracle 11g to Oracle 12c. To guarantee a smooth transfer, I first made a backup of the data in case of any problems during the upgrade. Then, before installing the most recent version of Oracle, I upgraded the database server’s operating system. Following these two procedures, I restarted the database server and tested it to ensure everything was operating well.

23. We Want To Be Certain That Our Database Security Is Top-Notch. What Security Precautions Would You Take?

To be able to manage their permissions, I would first create user accounts for each person who needs access to the database. To ensure that only authorized users can access the data, I will additionally set up password protection. I’ll also encrypt the data to keep it safe in transit and at rest. Last but not least, I’ll routinely back up the database to guard against data loss.

24. Describe The Steps You Take To Back Up Your Databases.

I use RMAN, an Oracle tool that executes logical and physical backups.  I make a copy-only backup of all the data files before taking a snapshot of the complete database. Then I back up all the archived redo logs with a copy. I create a copy-backup of the control files and the parameter file. I perform these backups and then store them in different places.

25. Which Programming Languages Do You Find Easiest To Use?

I like working in PL/SQL and Java because they are the most efficient when interfacing with the Oracle database. For instance, I can write code that runs on the server side because I utilize PL/SQL to build stored procedures and functions inside the database. I also create web applications that communicate with the Oracle database using Java.

Conclusion

You must have a thorough understanding of the Oracle database architecture and be able to efficiently administer and monitor the database’s performance if you want to succeed in this position. Additionally, you’ll need to be familiar with Oracle RAC, Oracle Data Guard, and Oracle GoldenGate.

If you are interviewing for an Oracle DBA position, you can anticipate questions about your knowledge of Oracle database technologies. You can be questioned about your knowledge of backup, recovery procedures and database management, and performance monitoring.