Is it necessary to be Unix Certified to become a good Oracle 9i DBA?

Answer

Oracle and UNIX are actually two separate things. Yes, Oracle was developed on UNIX, but it doesn't require UNIX to run. You can run Oracle on Windows (although, I don't recommend it). I have worked with DBAs who know very little about UNIX and usually relied on me (UNIX Systems Admin) to help them out with the UNIX stuff.

That said, I will say this. It is in your best interest to understand UNIX as much as possible in your role as DBA. The reason, there are a lot of under-the-hood system/kernel enhancements that can be made to UNIX that can significantly speed up the performance of Oracle (this can be said of Windows, to some degree, as well). This knowledge also makes you more valuable to an employer, but not necessarily monetarily. It also makes you less reliant on UNIX Admins for knowledge. Also, the more self-sufficient you are, the more valuable you are as an employee.

I would suggest you install Linux at home on some kind of hardware and then get Oracle 9 to install on Linux. If you can't get Oracle 9, you can always try MySQL. This at least gets you familiar with building a database on UNIX (along with SQL and networking). Most of this knowledge is easily applied to Oracle with the exception of Oracle specific things.

As far as certifications go, that's up to you. Employers like certificates because it says that you are up-to-speed on the newest stuff. However, as with any certification, your knowledge may vary. To get into the real nitty-gritty of an OS really requires a lot more knowledge than what certification tests require... and is usually the level you need when doing advanced troubleshooting.

Good luck.