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v$buffer_pool学习

原创 Linux操作系统 作者:haha牛 时间:2012-03-07 16:16:58 0 删除 编辑

此视图用于描述buffer_pool的信息

V$BUFFER_POOL displays information about all buffer pools available for the instance.

Column Datatype Description
ID NUMBER Buffer pool identifier number
NAME VARCHAR2(20) Name of the buffer pool:
  • DEFAULT

  • KEEP

  • RECYCLE

    Note: Currently, KEEP and RECYCLE pools only exist for the standard block size. All non-standard block size pools are DEFAULT.

BLOCK_SIZE NUMBER Block size (in bytes) for buffers in this pool. Possible values: the standard block size, the power of 2 non-standard block sizes, 2048, 4096, 8192, 16384, 32768.
RESIZE_STATE VARCHAR2(10) Current state of the resize operation:

STATIC - Not being resized

ALLOCATING - Memory is being allocated (can be cancelled by the user)

ACTIVATING - New buffers are being created (user cannot cancel)

SHRINKING - Buffers are being deleted (can be cancelled by the user)

CURRENT_SIZE NUMBER Present size of the sub-cache (in megabytes)
BUFFERS NUMBER Current instantaneous number of buffers
TARGET_SIZE NUMBER If a resize is in progress (state is not STATIC), records new target size (in megabytes). If the pool is STATIC, the value in this column is the same as the current size of the pool.
TARGET_BUFFERS NUMBER If a resize is in progress, records new target size in terms of buffers. Otherwise, the value in this column is the same as the current number of buffers.
PREV_SIZE NUMBER Previous buffer pool size. If the buffer pool has never been resized, the previous size is zero.
PREV_BUFFERS NUMBER Previous number of buffers in the buffer pool. Value is zero if the buffer pool has never been resized.
LO_BNUM NUMBER Obsolete column
HI_BNUM NUMBER Obsolete column
LO_SETID NUMBER Obsolete column
HI_SETID NUMBER Obsolete column
SET_COUNT NUMBER Obsolete column

1、在name列中的keep和recycle只针对于标准数据块大小的缓冲区有值。不支持非标准块,标准块就是block_size参数对应的大小。

2、RESIZE_STATE代表这块缓冲区的当前动作,STATIC 表示无动作;ALLOCATING 表示此缓冲区正在分配中,此时用户可以取消此操作;ACTIVING表示此缓冲区已经分配完毕,正在使用中,用户不能取消分配操作;SHRINKING 表示正在收回分配的缓冲区,用户可以取消操作。

3、CURRENT_SIZE个人理解为自动内存管理时,各数据缓冲区的大小。

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/23655288/viewspace-717954/,如需转载,请注明出处,否则将追究法律责任。

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