I'm now starting to self study the 8i exams and not yet take any related exam. The question is I'm afraid after I prepared & going to take exams but Oracle say 9i is recommended and 8i exams are no longer available.
So do I have to wait for 9i exams or go ahead to study 8i?
I feel better o ahead with Oracle 8i as you are preparing for it. It will take allmost about 6 months for oracle to start exams on Oracle 9i once you finish oracle 8i you can allways take one paper of oracle 9i to upgrade to 9i then you would be certified in both 8i as well as 9i.
If you are preparing for OCP in Oracle DBA you do the following complete tracks: Oracle 8 or Oracle 8i.
If you are already OCP for Oracle 7 DBA you can do the upgrade to Oracle 8 (1Z0-010), this exam is also part of the Oracle 8 DBA track so it will stay around untill this track is retired.
If you are OCP for Oracle 8 you can do the upgrade to Oracle 8i (1Z0-020), this exam is part of both the Oracle 8 DBA track as the Oracle 8i DBA track.
Also there is the Oracle 8i mix path track in which you can mix Oracle 8 and 8i exams supplementing it with the Oracle 8i upgrade exam (1Z0-020).
The Oracle 9i track will start in a Beta version before the end of this year probably this track will contain an upgrade exam.
My advise would be take OCP on the database version you are currently working on and do the upgrade exam when you migrate/upgrade your database to the new version so you can get some hands on experience