Oracle教程 2023-02-24

Oracle 视图 DBA_HIST_LATCH_MISSES_SUMMARY 官方解释，作用，如何使用详细说明

本站中文解释

Oracle视图DBA_HIST_LATCH_MISSES_SUMMARY报告的是系统到目前为止运行的汇总锁等待次数。这些等待次数将用于确定是否存在某种锁定冲突，以及系统可能在特定的锁定保持时间内存在何种瓶颈。不同类型的锁定过程（如读锁、写锁等）也有不同的等待时长，这可以帮助用户更好地分析和诊断因锁而导致的系统性能问题。

使用DBA_HIST_LATCH_MISSES_SUMMARY视图的步骤如下：

1.连接Oracle数据库，登陆到一个特定的用户帐户。

2.使用带有查询条件的SELECT语句查询DBA_HIST_LATCH_MISSES_SUMMARY视图，以获取所需的汇总记录。

3.使用有选择性的GROUP BY语句对DBA_HIST_LATCH_MISSES_SUMMARY视图中的数据进行分组，以获取不同类型的锁定汇总信息。

4.使用带有ORDER BY语句的SELECT语句来根据需要对DBA_HIST_LATCH_MISSES_SUMMARY视图中的结果进行排序和筛选。

5.关闭Oracle数据库。

官方英文解释

DBA_HIST_LATCH_MISSES_SUMMARY displays historical summary statistics about missed attempts to acquire a latch.

This view contains snapshots of V$LATCH_MISSES.

Column	Datatype	NULL	Description
`SNAP_ID`	`NUMBER`	`NOT NULL`	Unique snapshot ID
`DBID`	`NUMBER`	`NOT NULL`	Database ID for the snapshot
`INSTANCE_NUMBER`	`NUMBER`	`NOT NULL`	Instance number for the snapshot
`PARENT_NAME`	`VARCHAR2(50)`	`NOT NULL`	Latch name of a parent latch
`WHERE_IN_CODE`	`VARCHAR2(64)`	`NOT NULL`	Location that attempted to acquire the latch
`NWFAIL_COUNT`	`NUMBER`		Number of times that no-wait acquisition of the latch failed
`SLEEP_COUNT`	`NUMBER`		Number of times that acquisition attempts caused sleeps
`WTR_SLP_COUNT`	`NUMBER`		Number of times a waiter slept
`CON_DBID`	`NUMBER`		The database ID of the PDB for the sampled session
`CON_ID`	`NUMBER`		The ID of the container that `CON_DBID` identifies. 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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