What is important is how good you understood the basics, diagnose the problems. This all comes from self interest.
I have come across many DBAs whos experience almost double than mine. They dont want to test new features, they simply dont want to take risks and etc.
By the way, at least I am not an Oracle export. I still learn a new thing everyday about Oracle. Whenever, I come to know a new thing in Oracle, I feel myself still new baby. I guess there is no end for learning, specially in Oracle.
If you spend some dedicated time with confidence, taking challenges, making Oracle DBA profession to your passion level, I guess, 2 - 3 years are good.
As you can see on my profile, I've been working with Oracle Database since version 8.0.5, I think since 1998. But as Syed said, what is important is how good you understood the basics and diagnose the problems. I'm not consider a Oracle Expert, you can see that I'm a OCA 9i yet, and I need study all day to improve my knowledge about Oracle technology. In order to resolve the problems, I think that the On-line Documentations are the first place that you need go.
>>But you having good knowledge about Oracle Database
Well, tank's Mohammad, I think that my humble knowledge about some topics about Oracle Database is a stimulation to learning more and more ....
>>you post is really very helpful for newbie and professional.
Tank's again. One tip: For a professionals that are beginning or that already work with Oracle Technology, I always advice, if possible (available time), to access the blogs or articles that many Oracle experts professionals, ACE members maintain on your sites.
Always is good to learn with someone that have more knowledge and experience than you. :-)
Sometimes, I write some "basic" articles about Oracle Database in order to spread the Oracle Database on my city, country, but also to expose what I learned.
If somebody will have curiosity, the link is http://www.rps.com.br/artigos (Brazilian Portuguese)
>>I go through mention link but sorry i have no idea about your local language.
he he :-), no problem! http://www.google.com/language_tools?hl=en (just kidding).
This is a site of a company that I work here in Brazil, and this is not a "global" site, then the managers said to me to write the articles in a Portuguese language.:-(
All our customers are Brazilians....