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V$LATCH_CHILDREN视图

http://docs.oracle.com/database/121/REFRN/refrn30109.htm

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V$LATCH_CHILDREN

V$LATCH_CHILDREN displays statistics about child latches. This view includes all columns of V$LATCH plus the CHILD# column. Note that child latches have the same parent if their LATCH# columns match each other.

ColumnDatatypeDescription
ADDRRAW(4 | 8)Address of the latch object
LATCH#NUMBERLatch number of the parent latch
CHILD#NUMBERChild latch number (unique only to each parent latch)
LEVEL#NUMBERLatch level
NAMEVARCHAR2(64)Latch name
HASHNUMBERLatch hash
GETSNUMBERNumber of times the latch was requested in willing-to-wait mode
MISSESNUMBERNumber of times the latch was requested in willing-to-wait mode and the requester had to wait
SLEEPSNUMBERNumber of times a willing-to-wait latch request resulted in a session sleeping while waiting for the latch
IMMEDIATE_GETSNUMBERNumber of times a latch was requested in no-wait mode
IMMEDIATE_MISSESNUMBERNumber of times a no-wait latch request did not succeed (that is, missed)
WAITERS_WOKENNUMBERThis column has been deprecated and is present only for compatibility with previous releases of Oracle. No data is accumulated for this column; it will always have a value of zero.
WAITS_HOLDING_LATCHNUMBERThis column has been deprecated and is present only for compatibility with previous releases of Oracle. No data is accumulated for this column; it will always have a value of zero.
SPIN_GETSNUMBERWilling-to-wait latch requests which missed the first try but succeeded while spinning
SLEEP[1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11]NUMBERThese columns have been deprecated and are present only for compatibility with previous releases of Oracle. No data is accumulated for these columns; they will always have a value of zero. As a substitute for these columns you can query the appropriate rows of the V$EVENT_HISTOGRAM view where the EVENT column has a value of latch free or latch:%.
WAIT_TIMENUMBERElapsed time spent waiting for the latch (in microseconds)
CON_IDNUMBERThe 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

ADDR： latch对象的物理地址。

LATCH#：子latch的父latch号。

CHILD#：子latch号，对于每一个父latch，子latch都是唯一的。

LEVEL#：latch级别。

NAME：latch名称。

HASH：latch哈希值。

GETS：在Willing-to-waits模式下请求latch次数。

MISSES：在Willing-to-waits模式下发生等待时请求latch次数。

SLEEPS：当发生latch等待导致session休眠时请求latch的次数。

IMMEDIATE_GETS：no-wait模式下请求latch次数。

IMMEDIATE_MISSES：请求no-wait latch失败的次数。

WAITERS_WOKEN：该列已经被当前版本弃用，保留是为了向前兼容。

WAITS_HOLDING_LATCH：该列已经被当前版本弃用，保留是为了向前兼容。

SPIN_GETS：当spinning时，最终成功请求Willing-to-wait latch次数

WAIT_TIME：latch等待消耗的时间（以微秒计算）。

CON_ID：表明数据的从属关系，0 表示那些行属于CDB的数据，1 表示仅属于root，n 表示适用的container ID。

 


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