Oracle DBA certifications have two levels, as far as I remember.
OCA and OCP.
OCA - SQL + Fundamentals 1
OCP - Fundamentals 2 + Performance Tuning
PL/SQL certifications are different.
You should check up Oracle.com for the exact details.
These certifications are good if you plan to make a career as a Oracle DBA.
I think you should give yourself 1-2 months for each paper if you're working full time.
HTH
AMIt
[ August 13, 2006: Message edited by: Amit Saini ]