Oracle教程 2023-02-24

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

Oracle视图V$LATCHNAME是内部视图，展示系统中所有可用的latch（锁）。每个latch都有唯一的名称（latchname），它可以帮助数据库管理员对数据库做出更好的调整，从而提高数据库性能。

使用方法：

1、可以使用以下sql语句查询V$LATCHNAME视图：

Select Latch#, Latchname, Gets, Misses, Sleeps From V$Latchname;

2、使用V$LATCHNAME视图，你可以获得某一个latch的 hits 计数，以及把latch等待的次数。所获得的信息可以用来判断某一个数据库的性能情况。

3、还可以使用V$LATCHNAME视图，对数据库中比较繁杂的操作手段进行跟踪。使用此视图，可以找出性能可能出现问题的latch，并且可以采取有效的优化措施。

V$LATCHNAME displays information about decoded latch names for the latches shown in V$LATCH.

The rows of V$LATCHNAME have a one-to-one correspondence to the rows of V$LATCH.

Column	Datatype	Description
`LATCH#`	`NUMBER`	Latch number
`NAME`	`VARCHAR2(64)`	Latch name
`DISPLAY_NAME`	`VARCHAR2(64)`	A clearer and more descriptive name for the latch that appears in the `NAME` column. Names that appear in the `DISPLAY_NAME` column can change across Oracle Database releases, therefore customer scripts should not rely on names that appear in the `DISPLAY_NAME` column across releases.
`HASH`	`NUMBER`	Latch hash
`TYPE`	`VARCHAR2(4)`	Type of the latch (`SGA`, `PDB`, or `OSP`):
`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