Re: Questions for a Jr. DBA

IMHO, the technique proposed by Tim is a good strategy if the main task of the recruit would be to conduct presentations or trainings.
However, if you are looking for a technical DBA whose main task is to interact with databases and other computer-based programs, this interview technique may well let you loose the best candidate, if he happens to lack the extrovert personality required to conduct an impromptu presentation on the innards of the Oracle Database. An introvert candidate, already nervous because of the interview, would probably lock up and spend 10 minutes drawing and say nothing... I know I would!
I concur with Andrew Kerber. If your aim is to hire a good DBA, irrespective of presentation skills, it is probably best to engage the candidate in a discussion on particular tricky events that have happened in previous positions/during the course (if the candidate has just graduated) and through that try and gauge the level of insight, skill and tenacity of the candidate. The questions listed by Andrew would be good focus points to lead the discussion.
Personally I question the sense of conducting an elaborate exam. Either the candidate is knowledgeable but flunks because of nervousness, or the candidate knows zilch, but has spent the previous evening memorizing the "2-day DBA" guide and is hired. You'd do better to rely on the OCP exams! In my opinion, if their CV shows the required experience and/or education, then that needs not be revisited and the interviewer can dive directly into a case study. If they have exaggerated their CV, then the ensuing discussion will quickly leave them out of their depth. In the unlikely event that they talk themselves out of it, their lack of knowledge will become apparent during the probation period.
Having said that, one tricky exam question that will separate the Oracle DBA's from the impostors is : "Explain the relation between Database, Tablespace and Datafile". The three terms have completely different meanings in different products and Oracle's use is quite unique in that there is only one database per instance, containing many tablespaces which own datafiles. It confuses even many developers.. :) 

Just my 2ct.

Cheers,
Tony

Tim Gorman wrote:
I believe the most useful interview strategy for DBAs, junior or senior, is to ask them to walk up the whiteboard and begin diagramming and explaining what the Oracle database is and how it works, and just keep going into detail where they feel comfortable until I ask them to stop.
Some people walk up, pick up a pen, and draw for 10 mins saying nothing. Others talk with their back to their interviewers. Others do a good job of explaining, using the whiteboard for emphasis, not as a crutch. Inevitably, something needs to be clarified or challenged or simply refuted, and it is very illuminating to see how the candidate deals with that.
I think this technique works for juniors, intermediates, and seniors. Pretty hard to hide knowledge or ignorance this way...
Along the way, the interviewer can ask questions like those below as well, if they wish. I think if it fits into context, it is less of an interrogation, and there is less emphasis on rote memorization? One thing is that I think candidates should be permitted the use of Google and online documentation, just as in real life, if they feel the need. 

Hope this helps...



On 2/6/2011 4:06 PM, Guillermo Alan Bort wrote:
So, I am in the process of reviewing resumes from several JR and SSR candidates for the team. The question I came up with is, what kind of questions (technical) should I ask during the interview. I can't use the same questions I'd use with a Sr. DBA. 

The questions i've come up with so far are the following:
1. Difference between EXTENT and BLOCK
2. Difference between USER and ROLE. When would you use each?
3. Command to extend a Tablespace (tricky question? should it be datafile?) 
4. Command to backup controlfiles (all you can think of)
5. Steps to switch archivelog on or off.
6. Minimum requirements in order to take a level 1 online backup (tricky question?) 7. What are the minimum required files to be backed up in order to be able to recreate the database from scratch in the event of complete media failure? 

I may come up with more, but that's what I have so far...

thanks in advance
Alan.-

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