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Common Problems Why Hard Disks Crash
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Learn How To Safely Backup Your Hard Drive
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Get Down With OCP: Evaluating DBA Job Applicants in an OCP World
Not long ago, weeding through DBA applicants with a tech interview was a straightforward process. You'd ask candidates 200 or so technical questions. If they got 100 correct answers, you knew they'd been around the block; 150 or more and you knew you were on to superior talent. But once the Oracle Certification Program (OCP) became popular in the late 90s, the traditional tech interview lost its effectiveness. These days, candidates can answer 180 questions correctly and you still won't know whether they're talking from experience or simply regurgitating what they memorized at OCP a few weeks earlier. Although it has become increasingly difficult to determine whether you've found a seasoned, highly qualified DBA or a newly minted OCP Graduate, there are ways.
First, start by throwing out the questions. Any candidate who has been through OCP knows the answers—all of them. That list that helped you find superstar employees in the past is unfortunately useless now. Second, if you are a manager without solid database experience, enlist the help of an experienced DBA to help you prepare that critical interview. IT Managers have varied backgrounds and here it's important to pull from the right background, be it yours or someone else's.
You also need to analyze your needs. If you're looking to hire a junior person and mentor them, the OCP program ensures that the candidate has been exposed to most areas of the Oracle RDBMS. You can assume you'll have an employee who knows the commands and has a general concept of how a database works. But if you select an inexperienced OCP candidate thinking you're getting a skilled veteran, you'll be in for countless unpleasant surprises. Typical horror stories sound like:
A DBA restores the backup for the first time in a real-life situation, finds out the backup strategy was flawed and loses the whole database. S/he probably also forgot to make a backup of the database before attempting the recovery, therefore rendering Oracle support intervention nearly impossible.
A DBA recommends technical implementation decisions based on limited experience with a single user database that has 10 tables of 100 rows each. Of course, the system hangs a few hours after the launch—as soon as 10,000 users start pounding on a 500GB database.
The most damaging aspect of newer DBAs is that they don't know when they are in over their heads, or how to plan properly. Senior IT professionals, no matter their field of expertise, have a gut feeling when it's happening. They know they have to step
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away, talk things over with a peer, roll everything back, and try another day. Inexperienced IT professionals are fearless and can therefore be dangerous, especially if they're expected to run the show.
So how do you find truly qualified DBAs in an OCP World? Put them to work—in the interview, that is. Create real world situations where candidates are allowed full use of any familiar online resources, and see what they can do. Some examples:
Want to check out their data modeling skills? Give candidates a hypothetical business that everyone understands, like a video rental store, and a basic set of business requirements. Put them in front of a white board and let them create a model that meets the stated requirements. You play the role of a subject-matter expert who is decidedly non-technical, and have them walk you through the results.
Wondering how they handle troubleshooting? Set up a database with various performance anomalies such as poorly written queries, missing indexes, and internal resource contention. Have applicants deal with the issues and walk you through their methodology. They can't use automated tools. The Oracle Data Dictionary and OS basic facilities must suffice.
Want to see if they know how to minimize downtime? Pretend you're a client who wants to upgrade a 500GB database from version X to version X+1. It's a 24/7 environment and each hour of downtime costs $10,000. There will be downtime regardless, but the DBA should be able to generate scenarios to keep it at a minimum.
Whatever skills you're looking to assess, make sure you test candidates in situations they can't prepare for and can't fake. The new interview process isn't quite as easy as those trusty old 200 questions. It requires more up-front planning and often more time in the interview room. But if it saves you from having to fire incapable employees who wreaked havoc on your database, it's probably worth it. A little advance preparation can save a whole lot of time, money, and hassle down the road. And isn't that all we're looking for in this crazy, mixed-up OCP world?
About the Author
Rob has served as the applications architect for one of the largest government databases in the world. Before joining The Pythian Group in 2000, he worked for numerous corporations and government agencies, including Human Resources and Development Canada and Elections Canada. An acknowledged expert in the field, Rob excels in application architecture and application performance tuning.
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