Friday, March 27, 2009

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 requestor 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]

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:%.

SLEEP[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.

WAIT_TIME

NUMBER

Elapsed time spent waiting for the latch (in microseconds)

See Also: "V$LATCH"

Oracle data dictionary views

Oracle dynamic performance views

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