Oracle教程 2023-03-25

Oracle 视图 V$BT_SCAN_CACHE 官方解释，作用，如何使用详细说明

V$BT_SCAN_CACHE视图是用来查看Oracle数据库系统中Block Table Scan（BTS）缓存信息的视图，该缓存用来提高查询性能，可以缓存查询操作针对表或者索引的扫描结果，例如聚簇表的全表扫描，索引的全索引扫描、使用索引的范围扫描等等。

使用V$BT_SCAN_CACHE视图，可以查看BTS缓存记录的信息，包括表名称、BTS操作类型、操作参数等内容，可以帮助我们判断是否需要更改优化器参数来调整BTS缓存的使用，从而提高查询性能。

V$BT_SCAN_CACHE shows the parameters and status of the big table cache section.

Column	Datatype	Description
`BT_CACHE_ALLOC`	`NUMBER`	Current ratio of the big table cache section to the buffer cache
`BT_CACHE_TARGET`	`NUMBER`	Target ratio of the big table cache section to the buffer cache
`OBJECT_COUNT`	`NUMBER`	Number of objects tracked by the big table cache section
`MEMORY_BUF_ALLOC`	`NUMBER`	Number of memory buffers allocated by the big table cache section to objects
`MIN_CACHED_TEMP`	`NUMBER`	Minimum temperature of any object that is allowed to be cached by the big table cache section
`CON_ID`	`NUMBER`	The ID of the container to which the data pertains. Possible values include: `0`: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs. `1`: This value is used for rows containing data that pertain to only the root n: Where n is the applicable container ID for the rows containing data