Oracle教程 2023-02-24

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

Oracle视图V$SYSTEM_WAIT_CLASS用来查看当前系统背景进程的等待事件分类和平均等待时间。
它的数据来源于V$SESSION_WAIT视图中包含的等待事件，它们在该视图中以平均,总数和最大形式分类显示出来，但这些所有的等待时间都被按照主要的等待队列类别进行分类。

用法：
可以使用下面的SQL查询语句来查看V$SYSTEM_WAIT_CLASS视图中的信息：
SELECT * FROM V$SYSTEM_WAIT_CLASS
ORDER BY TOTAL_WAITS DESC;

此查询语句将结果按照总等待次数（TOTAL_WAITS）降序排列，显示出最消耗系统资源最严重的等待类别。

V$SYSTEM_WAIT_CLASS displays the instance-wide time totals for each registered wait class.

Column	Datatype	Description
`WAIT_CLASS_ID`	`NUMBER`	Identifier of the wait class
`WAIT_CLASS#`	`NUMBER`	Number of the wait class
`WAIT_CLASS`	`VARCHAR2(64)`	Name of the wait class
`TOTAL_WAITS`	`NUMBER`	Total number of waits from this wait class
`TIME_WAITED`	`NUMBER`	Total amount of time spent in waits from this wait class (in hundredths of a second)
`TIME_WAITED_MICRO`	`NUMBER`	Total amount of time spent in waits from this wait class (in microseconds)
`CPU`	`NUMBER`	Total amount of CPU time consumed while implementing waits from this wait class (in microseconds)
`TOTAL_WAITS_FG`	`NUMBER`	Total number of waits for this wait class, from foreground sessions
`TIME_WAITED_FG`	`NUMBER`	Total amount of time spent in waits from this wait class, from foreground sessions (in hundredths of a second)
`TIME_WAITED_MICRO_FG`	`NUMBER`	Total amount of time spent in waits from this wait class, from foreground sessions (in microseconds)
`CPU_FG`	`NUMBER`	Total amount of CPU time consumed while implementing waits from this wait class, from foreground sessions (in microseconds)
`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

Note:

This view returns instance-wide data and a value of 0 in the CON_ID column when queried from the root of a CDB.

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