This artical is forcused on Oracle 11g Release 2.  It is an summary from the OCP documentation. The topics discussed here including tunning memory, tunning sql, tunning segment access, identifing objects that are invalid or unusable and using Database Replay facility to generate workload for testing.

Memory management
SQL tunning
Segment access tunning
Invalid or unusable object identifing

Memory management

Memory mangement in Oracle including PGA management and SGA management. In oracle 9i, PGA is auto-managemed, in 10g SGA is auto-managed, in 11g PGA and SGA can be managed automatically together.

PGA Memory Management

Before talking about PGA, we presume that you already know the releationship between server process , user process and session. PGA is used by the server process to store session – specific data including:

temporary tables
sorting rowsi`m not sure here. shouldn`t the sorting rows and temporary tables be stored in temple tablespace?)
merging bitmaps
variables
the call stack

For some data in the PGA, use of memory is nonnegotiable. For example, if the session needs memory for its call stack, that memory must be made available. For other structures such as temporary table storage) use of PGA is nice but not essential, because if necessary the data can be written out to a disk-based storage structure— though this will impact adversely on performance.