Oracle’s 9i OCA (Oracle Certified Associate) DBA (Database Administrator) certification is for “apprentice skill level†IT professionals who have “have a foundation of knowledge that will allow them to act as a junior team member working with database administrators or application developers.†The Oracle 9i OCA was introduced in late 2001 and will likely stay very popular until the arrival of the Oracle 10g certification. There is no specific prerequisite for this certification; however, having some hands on experience with both SQL and an Oracle or other competitor database would definitely help.
This certification is well suited to IT personnel, with titles such as database administrator, database analyst, and database developer. The Oracle 9i OCA designation is achieved by passing two exams. If you choose the newer version of one of the exams, you must take it online.
Although Oracle certification paths eventually retire, you may continue to use a retired designation as it denotes the version of Oracle it is associated with. Also, Oracle normally provides a one exam upgrade to a newer version of a particular certification.
For more information:
http://www.oracle.com/education/certification/index.html?dba9i_oca.html
CORE EXAMS
(1Z0-001) SQL and PL/SQL 
(1Z0-007) Introduction to SQL 
(1Z0-031) DBA Fundamentals I