Memory Structures in Oracle Database

Memory Structures in Oracle Database include,

1. System Global Area( SGA)

2. Program Global Area (PGA)

Lets understand these memory structures in detail.

1. System Global Area( SGA)

The memory structure that contains the data and control information of one database instance is the System Global Area (SGA). Whenever you start a database instance, SGA memory allocated will be displayed. SGA is shared by both server and background process.

SGA contains below mandatory components

a) Shared Pool

b) Database Buffer Cache

c) Redo Log Buffer

d) Large Pool

e) Streams Pool

f) Java Pool

2. Program Global Area (PGA)

The memory structure that contains the data and control information of one server or background process is the Program Global Area (PGA). PGA is a non-shared memory region to which only one single process would be able to write  and it is exclusively for that process. Whenever a user session is created, PGA will be allocated.

PGA contains the following components

a) User Global Area ( UGA)

b) Stack Space

c) Hash Area

d) Bitmap Merge Area