http://docs.oracle.com/database/121/REFRN/refrn30109.htm
V$LATCH_CHILDREN
V$LATCH_CHILDREN displays statistics about child latches. This view includes all columns of V$LATCH plus the CHILD# column. Note that child latches have the same parent if their LATCH# columns match each other.
| Column | Datatype | Description |
|---|---|---|
ADDR | RAW(4 | 8) | Address of the latch object |
LATCH# | NUMBER | Latch number of the parent latch |
CHILD# | NUMBER | Child latch number (unique only to each parent latch) |
LEVEL# | NUMBER | Latch level |
NAME | VARCHAR2(64) | Latch name |
HASH | NUMBER | Latch hash |
GETS | NUMBER | Number of times the latch was requested in willing-to-wait mode |
MISSES | NUMBER | Number of times the latch was requested in willing-to-wait mode and the requester had to wait |
SLEEPS | NUMBER | Number of times a willing-to-wait latch request resulted in a session sleeping while waiting for the latch |
IMMEDIATE_GETS | NUMBER | Number of times a latch was requested in no-wait mode |
IMMEDIATE_MISSES | NUMBER | Number of times a no-wait latch request did not succeed (that is, missed) |
WAITERS_WOKEN | NUMBER | This column has been deprecated and is present only for compatibility with previous releases of Oracle. No data is accumulated for this column; it will always have a value of zero. |
WAITS_HOLDING_LATCH | NUMBER | This column has been deprecated and is present only for compatibility with previous releases of Oracle. No data is accumulated for this column; it will always have a value of zero. |
SPIN_GETS | NUMBER | Willing-to-wait latch requests which missed the first try but succeeded while spinning |
SLEEP[1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11] | NUMBER | These columns have been deprecated and are present only for compatibility with previous releases of Oracle. No data is accumulated for these columns; they will always have a value of zero. As a substitute for these columns you can query the appropriate rows of the V$EVENT_HISTOGRAM view where the EVENT column has a value of latch free or latch:%. |
WAIT_TIME | NUMBER | Elapsed time spent waiting for the latch (in microseconds) |
CON_ID | NUMBER | The ID of the container to which the data pertains. Possible values include:
|
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。
