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

本站中文解释

Oracle 视图 V$LATCH_MISSES 显示了服务器状态下的等待的 latch 请求的总数,它是试图申请 latch 的数量减去成功申请 latch 的数量,该视图帮助检测性能问题,这也可以帮助把经常发生 latch 失败的语句缩短时间,从而提高整体性能。

使用 V$LATCH_MISSES 时,可以与 V$SESSION 中的会话相关联,以了解哪些性能问题是由哪个用户引起的。借助这个视图,管理员可以收集以下有关任何进程OLS或会话的数据:

-Latch misses: V$LATCH_MISSES 中的 MISSES 列实际上代表了由用户引起的 latch 失败操作数
-Latch name: V$LATCH_MISSES 还返回确切的 latch 名称,可以帮助开发人员识别哪些 latch 请求没有完成,从而可以在应用程序级别上解决它
-SQLID:由 V$SESSION 表的 sql_id 列确定,以获取特定的 SQL 语句引起的 latch 失败。

通过使用 V$LATCH_MISSES,可以輕鬆識別 latch 保持失败的位置,并开始优化系统性能。

官方英文解释

V$LATCH_MISSES displays statistics about missed attempts to acquire a latch.

Column Datatype Description

PARENT_NAME

VARCHAR2(64)

Latch name of a parent latch

WHERE

VARCHAR2(80)

This column is obsolete and maintained for backward compatibility. The value of this column is always equal to the value in LOCATION.

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

LONGHOLD_COUNT

NUMBER

Number of times someone held a latch for the entire duration of someone else’s sleep

LOCATION

VARCHAR2(80)

Location that attempted to acquire the latch

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


数据运维技术 » Oracle 视图 V$LATCH_MISSES 官方解释,作用,如何使用详细说明