System Global Area (SGA) 系统全局区
The SGA is a group of shared memory structures, known as SGA components, that contain data and control information for one Oracle Database instance. The SGA is shared by all server and background processes. Examples of data stored in the SGA include cached data blocks and shared SQL areas.
Program Global Area (PGA)
A PGA is a memory region that contains data and control information for a server process. It is nonshared memory created by Oracle Database when a server process is started. Access to the PGA is exclusive to the server process. There is one PGA for each server process. Background processes also allocate their own PGAs. The total PGA memory allocated for all background and server processes attached to an Oracle Database instance is referred to as the total instance PGA memory, and the collection of all individual PGAs is referred to as the total instance PGA, or just instance PGA.
PGA是一个包含某一个服务器进程的数据和控制信息的内存区域.是一个非共享的内存区域当服务器进程启动的时候.PGA只能被一个服务器进程访问.没一个服务器进程都有一个PGA.后台进程也会有他们自己的PGA.全部PGA的区域包含后台和服务器进程是由PGA Memmory来决定的.所有PGA的集合是 实例PGA,
Figure 6-1 illustrates the relationships among these memory structures.
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