Memory Structures

Oracle's memory structure consists of two memory areas known as the System Global Area (SGA) and the Program Global Area (PGA) (see Figure 1.3).

Figure 1.3. Memory structures and processes of Oracle.

System Global Area

The SGA is the shared memory region that contains both data and control information for one Oracle instance. If there is more than one user connect to the instance, the SGA and the data allocation in the SGA are shared among all connected users. For this reason the SGA is often referred to as the Shared Global Area. Oracle allocates the entire SGA when an instance starts and deallocates the memory (freeing it for ...

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