Limiting the Size of the SGA (96)

The SGA_MAX_SIZE initialization parameter specifies the maximum size of the System
Global Area for the lifetime of the instance. You can dynamically alter the initialization
parameters affecting the size of the buffer caches, shared pool, large pool, Java pool,
and streams pool but only to the extent that the sum of these sizes and the sizes of the
other components of the SGA (fixed SGA, variable SGA, and redo log buffers) does not
exceed the value specified by SGA_MAX_SIZE.

If you do not specify SGA_MAX_SIZE, then Oracle Database selects a default value that
is the sum of all components specified or defaulted at initialization time. If you do
specify SGA_MAX_SIZE, and at the time the database is initialized the value is less
than the sum of the memory allocated for all components, either explicitly in the
parameter file or by default, then the database ignores the setting for SGA_MAX_SIZE.

限制SGA的大小
1. 當oracle初始化啟動時,如果sga_max_size的值小於顯式的指定的各sga元件值之和,則oracle將
會忽略sga_max_size
2. 當oracle初始化啟動時,如果sga_max_size小於sga_target時,啟動之後,sga_max_size將等於
sga_target
3. 啟動之後,sga_target就不能大於sga_max_size.

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