Oracle 视图 DBA_HIST_LATCH_CHILDREN 官方解释，作用，如何使用详细说明
本站中文解释
Oracle DBA_HIST_LATCH_CHILDREN视图查询有关每个数据库内部细微对象（如事务空间准备页、回滚段控制块）的性能计数器历史信息。通过检查这些计数器，您可以确定哪些缓存细分段正在活动检查或磁盘I/O，以及有多多久没有被访问以来。
这个视图在数据库性能调优中应用广泛，它可以帮助DBA发现当前与数据库内部细微对象有关的性能问题。使用视图检查分段和数据文件，可以帮助您确定哪些索引或哪些表是数据库性能瓶颈，也可以帮您发现哪些索引或表最少使用。
使用步骤：
1.使用SQL Worksheet打开Oracle数据库。
2.使用以下SQL查询检索详细历史细微对象的相关性能计数器信息:
SELECT * FROM DBA_HIST_LATCH_CHILDREN;
3.检查结果以获取有关缓存细分段访问的活动检查和磁盘I/O的相关信息。
官方英文解释
DBA_HIST_LATCH_CHILDREN displays historical statistics about child latches.
This view includes all columns of DBA_HIST_LATCH plus the CHILD# column. Note that child latches have the same parent if their LATCH# columns match each other. This view contains snapshots of V$LATCH_CHILDREN.
| Column | Datatype | NULL | Description |
|---|---|---|---|
|
|
|
|
Unique snapshot ID |
|
|
|
|
Database ID for the snapshot |
|
|
|
|
Instance number for the snapshot |
|
|
|
|
Latch hash |
|
|
|
|
Latch name |
|
|
|
|
Child latch number (unique only to each parent latch) |
|
|
|
Number of times the latch was requested in willing-to-wait mode |
|
|
|
|
Number of times the latch was requested in willing-to-wait mode and the requester had to wait |
|
|
|
|
Number of times a willing-to-wait latch request resulted in a session sleeping while waiting for the latch |
|
|
|
|
Number of times a latch was requested in no-wait mode |
|
|
|
|
Number of times a no-wait latch request did not succeed (that is, missed) |
|
|
|
|
Number of willing-to-wait latch requests which missed the first try but succeeded while spinning |
|
|
|
|
These columns have been deprecated and are present only for compatibility with previous releases of Oracle. No data is accumulated for these columns; they will always have a value of zero. |
|
|
|
|
Elapsed time spent waiting for the latch (in microseconds) |
|
|
|
|
The database ID of the PDB for the sampled session |
|
|
|
|
The ID of the container that
|
See Also:
-
“DBA_HIST_LATCH”
-
“V$LATCH”
