[This is a frequently discussed topic. Here's some input contrary to common answers.
Rewrite from 
http://www.freelists.org/post/oracle-l/Certifications-dont-count-from-one-who-has-none,2]

One coworker got into the DBA group partly because she's an excellent exam taker. She told me she 
never touched the database even once and passed OCP with high scores many years ago. This is a 
classic example any DBA group should reject accepting. But I disagree. A PhD in Biology, a top 
graduate from the top Chinese college, this person has extraordinary intelligence, excellent 
general troubleshooting skills and insight, and great dedication to work. It's true that knowledge 
helps solve problems. But in case you haven't noticed, a lot of real problems are solved with basic 
knowledge and a great deal of common sense. Take the issue of a missing synonym as an example. It's 
simple by itself. But triage of the problem in a complicated environment and narrowing it down to a 
missing synonym needs general intelligence and clear logical thinking. This person earned a great 
deal of credit from application teams by solving many of these production problems that don't need 
a true Oracle expert.





Appendix:

Difference between using insight and using knowledge to solve a problem

Using insight:

C:\temp>del test.txt
C:\temp\test.txt
Access is denied.
Check the file attribute. Aha, it's set to Read-only.

Using knowledge:

C:\temp>del test.txt
C:\temp\test.txt
Access is denied.
C:\temp>strace cmd /c del test.txt | grep STATUS
Access is denied.
...
483 1060 428 NtSetInformationFile (76, 1241211, 1, Disposition, ... ) == STATUS_CANNOT_DELETE
Look up "STATUS_CANNOT_DELETE" on Google and the first hit lists three possibilities returning this 
status. One of them is read-only file.