Adding Granules and Tracking Component Size (78)

最新推荐文章于 2025-12-20 13:10:13 发布

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本文介绍了如何使用ALTER SYSTEM语句调整Oracle数据库SGA中各组件的大小。通过修改与各组件相关的初始化参数，数据库会自动调整到最接近的16MB倍数。文章还提供了查询SGA信息及调整历史的方法。

A database administrator expands the SGA use of a component with an ALTER
SYSTEM statement to modify the values of the initialization parameters associated
with the respective components. Oracle Database rounds up the newly specified size
to the nearest multiple of 16MB and adds or removes granules to meet the target size.
The database must have enough free granules to satisfy the request. As long as the
current amount of SGA memory is less than SGA_MAX_SIZE, the database can allocate
more granules until the SGA size reaches SGA_MAX_SIZE.
The granule size that is currently being used for the SGA for each component can be
viewed in the view V$SGAINFO. The size of each component and the time and type of
the last resize operation performed on each component can be viewed in the view
V$SGA_DYNAMIC_COMPONENTS. The database maintains a circular buffer of the last
400 resize operations made to SGA components. You can view the circular buffer in the
V$SGA_RESIZE_OPS view.
Note: If you specify a size for a component that is not a multiple of
granule size, then Oracle rounds the specified size up to the nearest
multiple. For example, if the granule size is 4 MB and you specify DB_
CACHE_SIZE as 10 MB, you will actually be allocated 12 MB.

通过alter system指定组件的大小时， Oracle添加移除细粒度来达到目标值，如果指定的值
不是granule size的倍数， Oracle将rounds the specified size up to the nearest
multiple .当总的sga内存小于SGA_MAX_SIZ时，数据库可以分配细粒度来达到该值。
细粒度的值可以通过V$SGAINFO来查询，每个组件的值可以通过V$SGA_DYNAMIC_COMPONENTS ,
通过V$SGA_RESIZE_OPS视图可以查询sga组件的操作

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