Re: Questions for a Jr. DBA

  • From: Stephane Faroult <sfaroult@xxxxxxxxxxxx>
  • To: cicciuxdba@xxxxxxxxx
  • Date: Mon, 07 Feb 2011 14:52:29 +0100

I've read all posts so far in this thread; I really like Tim's approach
("explain to me how all this works"), although I agree there is some
truth in the argument that some good candidates may be too nervous or
impressed or simply bad communicators and give an impression that
doesn't truly reflect their abilities. Although as Martijn pointed out,
communication is key. I know a DBA (not a junior one) who is quite
competent but who, when meeting developers, only talks about cache
buffer chain latches and scattered read events - someone is always
required for translating what he says into something that developers can
relate to their code. As far as issue solving is concerned, someone less
competent but who communicates better may be more useful.

I think that your list looks too much like what I have seen of OCP
questions and the like - where you are supposed to provide THE good
answer (and I must admit that very often I have no idea of what kind of
"good answer" is expected). I think it would be more to the point to
confront candidates to some kind of practical situations, and ask them
how they would solve them (and I think that they should be made aware
from the start that "I call a senior DBA" is an option - it's important
to know one's limits before you make things worse).

To review your list, I think that rather than your first question I'd
rather tell a story of much slower performances since an event (table
used as a FIFO, reader process was down for x hours), and see whether
the candidate comes to anything looking like a HWM issue. Even if he or
she has a patchy knowledge of Oracle internals, seeing how a candidate
thinks and diagnoses is interesting. Or something about chaining. And I
would definitely give good marks to someone who would honestly tell me
they don't know enough yet to diagnose.
You often learn more about someone's abilities by their questions rather
than their answers.

For your question 2, I'd rather say "you need to create an account for
Ms XX who needs to have the same privileges as her colleague Mr XY" -
and see if roles come spontaneously on the table.

For 3, I'd go for the "Cannot allocate extent in tablespace ..." and ask
them what they would do. And so on.

Backups are a bit special. But you can ask them to discuss hot and cold
backup, what you can hope to recover in such or such case and so on.

But as others have said, it's more the appetite to learn and the
readiness to search the docs that count ...

My EUR 0.02.
Stephane Faroult
RoughSea Ltd <>
Konagora <>
RoughSea Channel on Youtube <>

On 02/07/2011 12:06 AM, 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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