Overview of the System Global Area (70)

A system global area (SGA) is a group of shared memory structures that contain data
and control information for one Oracle database instance. If multiple users are
concurrently connected to the same instance, then the data in the instance’s SGA is
shared among the users. Consequently, the SGA is sometimes called the shared global
area.
An SGA and Oracle processes constitute an Oracle instance. Oracle automatically
allocates memory for an SGA when you start an instance, and the operating system
reclaims the memory when you shut down the instance. Each instance has its own
SGA.

SGA
一組共享的包含資料和控制資訊的記憶體結構 ， Oracle例項由sga和Oracle程式組成 。
當例項啟動時 ，Oracle自動分配記憶體 ， 例項shutdown時 ， 作業系統回收記憶體 。

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