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The SGA_TARGET Initialization Parameter (74)

原创 IT综合 作者:tsinglee 时间:2007-10-23 10:47:44 0 删除 编辑

The SGA_TARGET initialization parameter reflects the total size of the SGA and
includes memory for the following components:
■ Fixed SGA and other internal allocations needed by the Oracle Database instance
■ The log buffer
■ The shared pool
■ The Java pool
■ The buffer cache
■ The keep and recycle buffer caches (if specified)
■ Nonstandard block size buffer caches (if specified)
■ The Streams pool
It is significant that SGA_TARGET includes the entire memory for the SGA, in contrast
to earlier releases in which memory for the internal and fixed SGA was added to the
sum of the configured SGA memory parameters. Thus, SGA_TARGET gives you precise
control over the size of the shared memory region allocated by the database. If
SGA_TARGET is set to a value greater than SGA_MAX_SIZE at startup, then the latter is
bumped up to accommodate SGA_TARGET.

SGA_TARGET : 指定sga的大小 , 包含以下组件
1. Oracle数据库实例需要的internal和固定SGA
2. 重做日志缓存区
3. 共享池 , java池 , 高速缓存等等
最后一句话的意思应该是实例启动时 ,当SGA_TARGET设置大于SGA_MAX_SIZE , 稍后
操作系统分配给Oracle内存将bumped up(突然增加)来适应SGA_TARGET


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