RE: DBA Interview Questions

Another thing I wanted to mention is it is very hard to find someone very knowledgeable in data warehousing. It is a totally different ball game and somebody who worked in OLTP and general purpose db's may not be a good fit for dw dba job. just my 2 cents... "Freeman, Donald" <dofreeman_at_state.pa.us> wrote:I like your approach. Since I prefer troubleshooting starting from a = user complaint instead of 'compulsive tuning' your progressive approach = makes sense.=20

-----Original Message-----
From: Post, Ethan [mailto:Ethan.Post_at_ps.net] Sent: Wednesday, November 24, 2004 2:57 PM To: dofreeman_at_state.pa.us; Oracle-L (E-mail) Subject: RE: DBA Interview Questions

I would propose two common scenarios...

1. Most users complain at unpredictable times about performance, how do you find the problem?
2. Single users complain about a specific form/screen with performance issues and problem is re-creatable, how do you find the problem?

These questions lead in to many others about performance tuning. I am basically looking for this...

1. Does the candidate have a good methodology for tracking overall system performance, setting up some type of "alert/capture" to tell them when a problem is occurring, and then responding to the alert or interpreting the captured info to determine what the problem is/was.
2. What tools does the candidate use (OEM, scripts, 10046, statspack), I will ask follow-up q's to ensure they actually use these tools.
3. Do they understand the wait interface, can the describe common wait events, problems with checkpointing too frequently, sizing methodologies for memory, redo logs etc...
4. Do they look at the OS level, iostat, sar, top, etc....
5. What resources do they use to troubleshoot other than standard (metalink), if they say oracle-l it is always a big plus!

I rate the interview on how much the candidate knows without being prompted or helped. I understand people get nervous and forget things and questions are usually skewed to my own knowledge so if they handle most of this stuff with even semi-reasonable responses I will usually recommend them for an interview.

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Freeman, Donald Sent: Wednesday, November 24, 2004 1:29 PM To: Oracle-L (E-mail)
Subject: DBA Interview Questions

We have a position open suddenly and I'll be participating in =3D interviewing my contract co-dba next week for a Oracle 9i data warehouse
=3D

position. One of the resumes I read mentioned the applicant had =3D experience in performance tuning by 'tuning buffer cache hit ratios' and
=3D

that made me want to buckle down and ask a few appropriate questions.

I first plan to ask what a buffer cache hit ratio is and then what a =3D 10046 trace is: If they can explain how to use it and explain waits =
=3D

then I'll know I've got a winner. =3D20

Whats the quickest way to find out if somebody knows something about =3D tuning? I'm just a novice myself and would like to be sure that the =
=3D

guy/gal we hire knows more than I do and can strengthen us in that area.
=3D

The guy we interviewed today didn't know what system stats and =3D histograms were and didn't know what RAC was. Hopefully we'll do =3D better next week when we resume. If anybody is interested in these =3D kind of contract positions you have to get on the list with Deloitte and
=3D

Touche. They are our primary contractors.=3D20

Don Freeman
Database Administrator 1
Pennsylvania Dept of Health
Bureau of Information Technology

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