I am basically a developer. I want to switch over to DBA side. I am confident about backup & recovery. But at the same time I want command over Database administration, performance tuning (topics/papers of OCP) such as SGA sizing etc.
1)How Oracle Database Engine internally process when you run a Query/Update/Delete/Insert.
2)How Oracle communicates from CLient to Server thru Middle tiers and what are the components involved
3)As for as Performance is concerned its on going process, you have to see where you have bottle necks, whiuch components of Oracle(Memory, I/O, RBS, REDO etc.,) making the response slow and start from there investigating and tuning.
Not mentioning anything about Backup and recovery as you know it.