Oracle教程 2023-04-03

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

本站中文解释

Oracle视图V$SES_OPTIMIZER_ENV，也叫做会话优化器环境视图，可以用来查看会话优化器使用的参数，包括本次会话使用的特定环境声明和系统优化器参数环境总览。

V$SES_OPTIMIZER_ENV用来查看每个会话的优化器环境，可以针对某个会话查看其环境变量的设置。该视图显示了每个会话被设置的优化器参数相关的信息。V$SES_OPTIMIZER_ENV包含的列包括：SES_ADDR、ACT_RESOLUTION、OPTIMIZER_ENV_HASH、ENV_KEY、ENV_VALUE和ENV_COMMENT，这些列描述了每个会话当前优化器参数被设置在什么环境中。

使用方法：以查询某个会话下所使用的优化器环境参数为例：

SQL> SELECT ses_addr, env_key, env_value
FROM v$SES_OPTIMIZER_ENV
WHERE ses_addr=’#####’;

官方英文解释

V$SES_OPTIMIZER_ENV displays the contents of the optimizer environment used by each session. When a new session is first created, it automatically inherits its optimizer environment from the optimizer environment defined at the instance level by V$SYS_OPTIMIZER_ENV. The value of certain parameters can be dynamically modified by issuing an ALTER SESSION statement.

Column	Datatype	Description
`SID`	`NUMBER`	Session identifier. This column can be used to join with `V$SESSION` on the `SID` column.
`ID`	`NUMBER`	Unique identifier of the parameter in the optimizer environment
`NAME`	`VARCHAR2(40)`	Name of the parameter
`SQL_FEATURE`	`VARCHAR2(64)`	Associated feature control ID
`ISDEFAULT`	`VARCHAR2(3)`	Indicates whether the parameter is set to the default value (`YES`) or not (`NO`)
`VALUE`	`VARCHAR2(25)`	Value of the parameter for the session
`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

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