自动管理方式：
调整两个参数：
SGA_TARGET and
PGA_AGGREGATE_TARGET initialization parameters.
做如下设置：
1、set the SGA_TARGET initialization parameter to a nonzero value
2、set the STATISTICS_LEVEL initialization parameter to TYPICAL or ALL.
3、应设置 SGA_MAX_SIZE ，在日后扩大内存时比较方便。
内存与操作系统的关系，为了避免页交换
应设置 LOCK_SGA
自动管理如下区：
Database buffer cache (default pool)
Shared pool
Large pool
Java pool
自动管理与手工管理的关系：如果手工设置了上面的值（即这些值非零），则这些值作为自动管理中的最小值，仍处在自动管理中。
SGA_TARGET 是个动态参数，可以在运行时进行调整，但不超过
SGA_MAX_SIZE。
手动管理，不受自动管理影响的部分：
Log buffer
Other buffer caches, such as KEEP, RECYCLE, and other block sizes
Streams pool
Fixed SGA and other internal allocations
这些区域所占用的大小会从总SGA中进行扣除。
操作语句：
example：ALTER SYSTEM SET
SGA_TARGET =10g SCOPE=SPFILE;
相关参数：
Automatically Sized SGA Components and Corresponding Parameters
SGA Component Initialization
The shared pool SHARED_POOL_SIZE
The large pool LARGE_POOL_SIZE
The Java pool JAVA_POOL_SIZE
The buffer cache DB_CACHE_SIZE
The Streams pool STREAMS_POOL_SIZE
影响范围：下次重启之后生效。 SCOPE=SPFILE 可选列表为：SPFILE,MEMORY,BOTH
参数值的粒度大小：
在小于1G时为4M；大于1G为16M
physical I/0慢的主要原因：
1、Disk access (physical I/O) take a significant amount of time,
compared with memory access, typically in the order of 10 milliseconds
2、Physical I/O also increases the CPU resources required,
2a、because of the path length in device drivers
2b、and operating system event schedulers.
V$SGA_CURRENT_RESIZE_OPS: Information about SGA resize operations that
are currently in progress. An operation can be a grow or a shrink of a dynamic
SGA component.
V$SGA_RESIZE_OPS: Information about the last 400 completed SGA resize
operations. This does not include any operations currently in progress.
V$SGA_DYNAMIC_COMPONENTS: Information about the dynamic components
in SGA. This view summarizes information based on all completed SGA resize
operations since startup.
V$SGA_DYNAMIC_FREE_MEMORY: Information about the amount of SGA
memory available for future dynamic SGA resize operations.
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