Explain the memory structure of Oracle.

We have two memory areas that comprise the memory structure of oracle.

System Global Area(SGA) : It is also called as Shared Global Area. It stores data and control information for the oracle server and can be shared by database processes.

Program Global Area(PGA) : It is also called as Process Global Area. It contains data and control information for a single server process.

Following are the structure contained in the SGA:

Shared pool: It stores most recently executed statements.
Database buffer cache: It stores copies of data block.
Redo log buffer: It records all changes made to the database blocks.
Large pool: It is optional area of the memory that can be used by the shared pool in order to relieve load on it.
Java pool: This area is used for parsing java command.