How to answer database slow question?

Question

Hi all,
In interviews I have seen people asking "Your database is slow, What will you do"? , this will be the question and there will not be any other inputs. When I ask on doing what are you hitting the performance problem, they come out telling "generally it is slow and now what will you do?" . Please let me know what should be the best answer for such questions? At first I thought the question is not a great one but as I can see many interviewers asking the same question again and again I started feeling this question is really logical.
Thanks,
Krishna

Answer 1

Well, the basic approach to tuning is
- Figure out what is slow
- Figure out why it's slow
- Figure out how to make it less slow
If the entire database is slow, you probably want to be looking at things like AWR or Statspack reports. Preferrably comparing current reports where the database is slow to prior points in time where similar workload was performing acceptably. When you identify the bottlenecks and the difference between today's slow performance and yesterday's acceptable performance, you'll know what to target.
Of course, this is a popular interview question precisely because it has a nearly infinite number of permutations. When you say that you'll look at an AWR report, for example, the interviewer can go in any number of directions. He (or she) might say that top wait event is sequential reads or RAC interconnect waits or any number of other possible causes. So you'll dig in and ask questions about, say, what SQL statements are accounting for the disk reads, whether the SGA or PGA advisors suggest that more SGA or PGA space might reduce I/O, etc.
Justin