Oracle DBA Interview Questions and Tips

It’s a topic that every Oracle DBA has asked themselves at one point or another “What questions will I be asked at my interview”. And wouldn’t we all like to know the answer to that one! Interviews can be tough and when it comes to Oracle DBA technical interviews the range of subject areas and different types of questions you can be asked about are pretty much infinite.

So, in truth, you will never know what questions you are going to be asked. Don’t worry, though, there are many ways to prepare and it is definitely possible to have an idea about what type of questions you will be asked and what areas of the Oracle stack they will cover.

DBA Interview Subjects

In this article I hope to help you to prepare for your interview and get you feeling confident that you have prepared as thoroughly as possible. Let’s start by listing some of the high level aspects of preparing for an interview and then we will go through them in more detail.

  1. Company Research -> Technologies used, OS platform, job spec, why they are employing someone, multinational
  2. Knowledge -> Re-read the concepts guide and other applicable guides, brush up on OCA/OCP knowledge
  3. DBA Basics -> RMAN strategies, patching, new features, space & user management, indexing, SQL, change management
  4. DBA Advanced -> Data Guard, RAC, HA solution, Golden Gate, SAN replication

OK, so there is a list of some areas which I want to cover and I believe that by using this as a guideline for your DBA interview questions you will be prepared for almost all questions. Now let’s take a more in depth look at each of the areas on the list, starting with the Company Research.

Company Research

Researching the company prior to going for your interview is absolutely essential. Imagine how it looks to your prospective employer if you can’t even do some basic research into their company; it gives the impression that you don’t care about your career and who you work for and/or that you don’t know how to handle yourself at an interview. Neither of which are good signs.

Doing appropriate research is not just about looking at their company website, it’s also about using social media and your contacts to find other useful information that is not available to everyone. You could check out if they have Linked-in, twitter and Facebook accounts and stay up-to-date with what they are doing. You can speak to colleagues and friends to see if anyone has information about the company that you are going for the interview with.

In addition to doing your research in this way, a great way to prepare for your interview is to ask the recruitment agent as many good questions as possible. The recruitment agent wants you to get the job, and they probably have a good working relationship with the company they are recruiting for so they should know a lot about their business. For example, you may ask some questions like the following:

  • Is the company expanding rapidly
  • Have they placed many Oracle DBAs there
  • Does the company have a high staff turnover
  • Do they know the employers well and what are they like
  • What technologies do the company use
  • What skills they are looking for their next Oracle DBA to have

There really are a lot of questions you can ask and you will gain some very valuable information from it.

Once you have gained the answers to some of these questions you will be able to prepare for your interview much more thoroughly and specifically. Let’s say that you find out they are a small to medium sized company who have an established market in the UK and are looking to expand into Europe. They run on the Windows platform and their system is available 24/7. From this you can deduce, if not already explicitly specified from the job specification, that they are likely to need someone who will know about replication and High Availability (HA) solutions. So you should go away and research some HA solutions and brush up on your replication knowledge, like Data Guard, Golden Gate or perhaps SAN based replication. You can also assume that there will be on-call work so you should add that to your list of questions to ask about.

Now let’s take a look at some knowledge that you must gain or refresh before you go for the interview

It’s all in the Know How

Although no one expects you to know everything there is to know about Oracle and how to be a master Oracle DBA, they will expect you to have a fundamental understanding of the key concepts when answering questions at the interview stage of the job application process. If you have read the Oracle concepts guide then you will know that there is a wealth of information in it. It’s not too in depth, but it’s also meaty enough to give you a good understanding of how the Oracle database works.

Hopefully you have already read this. If you have, great, read it again and I guarantee that you will learn something new. If not, you’d better get reading because there is a lot to learn. After reading, understanding and applying what is in the guide you should be very well prepared for a lot of the questions that they will ask you at the interview stage.

It’s also a good idea to branch out from the concepts guide and read some of the other Oracle documentation which is specific to the technologies they use at the company. If you know what technologies they use then you should plan your reading around this. If they are using Data Guard, make sure you understand how it works, what options there are and if possible what version they are running. You can look up the new features for a more recent version of the database and talk about them at your interview. You can read guides like the Data Guard Administration Guide and Data Guard Broker to gain a better understanding of it.

OCA & OCP Qualifications

If you have got an OCA/OCP qualification then you should be able to back this up with the knowledge to support that claim. It’s no use if you have the qualification but have forgotten all of the information. Brush up on that information before you go to the interview. If you don’t have the qualification then hopefully you are working towards it and can say that in your interview, and say that it’s your goal to study towards it.

When I interview someone, I often take questions from the OCA/OCP guides because the questions in there are usually fundamental to understanding how the database works. If someone who has the qualifications can’t answer a lot of the questions that are taken from the book during an interview then it makes me question exactly how good they are.

Now that we’ve established what kind of basic knowledge you need to have before going for your Oracle DBA interview, let’s take a look at some more Oracle DBA specific skills which you need to know to make you look like a good DBA.

DBA Basics

Once you have mastered the fundamental skills, which are also closely linked with the Oracle DBA basic skills, you should be a in a good position to answer most Oracle related questions at your interview. The basic skills that I am referring to within the Oracle DBA sense include the following:

  • RMAN backup strategies
  • RMAN restore and recovery processes
  • Patching and upgrading the database
  • Oracle new features
  • Space and user management
  • How indexes work and why you use them
  • Basic SQL statements and PL\SQL programming
  • Shell/dos scripting
  • Change management processes
  • Security best practices

You need to be able to demonstrate that you have these skills throughout your interview, or at least have some knowledge of the skills, to show that you understand and have learned how to become a successful and trustworthy Oracle DBA. After all, your prospective employer is putting a huge amount of trust in you to look after their most prized possession – their data!

The key to understanding the basics is doing. You can read about it as much as you like and this will help to some extent but the act of doing will speed up your learning massively. Ideally you would already be working within an Oracle DBA team where you are practicing these skills every day. If not, you need to start setting up some experiments and tests to get to grips with them and become good.

Run through the documentation and then try to carry out the tasks which are described. For example, try deleting a control file and recovering from the loss of it. Perhaps remove a datafile from a tablespace and see what happens. Make sure that you have backed up the database and that you can recover from it if necessary. All of these skills are essential and will most likely be asked about in one form or another at your interview. Now let’s take a look at some more advanced topics in the Oracle DBA world.

Advanced DBA Skills

You’ve done your research on the company you are interviewing at, you’ve got the knowledge from the concepts guide and you’ve mastered the basic Oracle DBA skills. Great work so far, you’re well on your way to acing that Oracle DBA interview and getting your dream job! Just a few hurdles left until you finally have your foot through the door. With that in mind, let’s start talking about some more advanced Oracle DBA skills.

There are many advanced DBA skills that you need to have, and with each job the required skill set will change. This is what keeps me entertained working as an Oracle DBA – if everything was the same all the time it would become very boring. What you will find is that once you have mastered the basics it is much easier to learn the advanced stuff. Sounds obvious but you’d be surprised how many people try to run before they can walk!

A few examples of the more advanced topics you should certainly be aware of;

  • Data Guard
  • RAC
  • SAN Replication
  • Golden Gate
  • High Availability solutions

Data Guard is definitely a good skill to master because there are a lot of shops out there who use it. It’s a great tool to use as a disaster recovery solution. It’s also good for high availability, as you can configure your standby database to failover automatically. So, you should definitely read up about Data Guard.

If you have not used Data Guard, that’s OK. You can very easily configure a physical standby database just as a test.

I have written another article about creating and configuring Data Guard so check that out, part way down the page.

I’d recommend starting with the Data Guard administration guide to get a feel for how it all works. By doing these tasks you will learn a lot about how everything fits together, what problems you are likely to face and the requirements for configuring the system.

A prospective employer is not going to expect you to know every Data Guard related command off the top of your head. What they are looking for is someone who has an appreciation for how it works, when you would use it and why you would use it. At the interview as long as you can put this across well and you’ve demonstrated that you have the ability to learn the other Oracle skills then they will be confident in your ability to learn the additional steps to configure Data Guard.

DBA Interview Tips

There are some other key points to note when going for an interview and I will start with the most important and that is, DO NOT LIE or make something up. I know it sounds obvious but it’s surprising how often candidates will attempt to answer every question even when they don’t know the answer. This is not a good idea. If someone tries to guess and answers incorrectly it will make the interviewer think they don’t know what they are talking about. The ideal response to make in this situation is to say “I’m sorry but I don’t know the answer. I would have to find out the answer from the documentation/Metalink/etc. What I do know is bla, bla, bla.”

If you don’t think you know the answer but you could have an educated guess then you should say you don’t know but you could take an educated guess and that you would have to look it up to confirm.

Ask questions. By asking questions you show your enthusiasm and interest in the job and company. It also shows the interviewer that you are taking the interview process seriously and that you are someone who wants to work at a place for more than just the money. And on that note, don’t just ask questions like how much you will get paid and what hours you have to work. I would recommend leaving these types of questions to the final interview.

At the first interview you should be asking questions to gain an insight into what the company is like, what systems they have, how large the team is, what other technical disciplines they have in-house, if they outsource any of their IT resources, what projects they have coming up, what gap they are trying to fill with the position they are interviewing for, etc. Be creative and show a genuine interest in the available job position.

Another very important point is that you should always back up your statements with examples/evidence from your work. For example, if you are describing what options you have for configuring a Data Guard configuration you could demonstrate your understanding by using a situation from your previous job where you configured Data Guard and why you used a particular setting

I hope that the information within this article has given you something to think about and reaslise that by learning your trade you will be more than prepared to answer any kind of question that the interviewer at your Oracle DBA interview can throw at you. If you don’t understand the question then don’t just guess away at an answer, be honest and say you don’t know the answer.

Good luck at that Oracle DBA interview!

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