Oracle教程 2023-04-03

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

Oracle视图V$IOSTAT_FUNCTION是一个视图，存储操作系统当前的 I/O 统计信息，它提供了一个简便的方法，用于查看系统 I/O 的实时统计数据，以及对统计数据进行分析。可以用它来找出在当前会话执行的任务中有意义的统计数据，并跟踪系统 I/O 活动状态，有助于查找性能瓶颈。

要使用V$IOSTAT_FUNCTION视图，可以用以下语句查询最新的I/O统计信息：

SELECT * FROM V$IOSTAT_FUNCTION ORDER BY SNAP_ID DESC;

这会显示该视图内的每列，并基于SNAP_ID对其进行排序，从而显示最新的I/O统计信息。

此外，也可以使用V$IOSTAT_FUNCTION视图来检查当前正在运行的查询的磁盘 I/O 情况。可以使用此视图提取有关某个工作负载或特定回话的磁盘 I/O 信息，这些信息可以用来分析具体的性能问题。

V$IOSTAT_FUNCTION displays disk I/O statistics for database functions (such as the LGWR and DBWR).

Column	Datatype	Description
`FUNCTION_ID`	`NUMBER`	Function ID
`FUNCTION_NAME`	`VARCHAR2(18)`	Function name: `RMAN` `DBWR` `LGWR` `ARCH` `XDB` `Streams` `AQ` `Data` `Pump` `Recovery` `Buffer` `Cache` `Reads` `Direct` `Reads` `Direct` `Writes` `Smart` `Scan` `Archive` `Manager` `Others`
`SMALL_READ_MEGABYTES`	`NUMBER`	Number of megabytes read via single block read requests
`SMALL_WRITE_MEGABYTES`	`NUMBER`	Number of megabytes written via single block write requests
`LARGE_READ_MEGABYTES`	`NUMBER`	Number of megabytes read via multiblock read requests
`LARGE_WRITE_MEGABYTES`	`NUMBER`	Number of megabytes written via multiblock write requests
`SMALL_READ_REQS`	`NUMBER`	Number of single block read requests
`SMALL_WRITE_REQS`	`NUMBER`	Number of single block write requests
`LARGE_READ_REQS`	`NUMBER`	Number of multiblock read requests
`LARGE_WRITE_REQS`	`NUMBER`	Number of multiblock write requests
`NUMBER_OF_WAITS`	`NUMBER`	Number of synchronous I/O waits by functionality
`WAIT_TIME`	`NUMBER`	Total synchronous I/O wait time (in milliseconds)
`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

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