Oracle 视图 V$PARAMETER2 官方解释，作用，如何使用详细说明

本站中文解释

Oracle视图V$PARAMETER2可以查看系统的所有参数，及参数的值、数据类型、服务级别、是否是只读参数等。通过V$PARAMETER2可以很方便的查看Oracle的参数的当前值并调整自身的数据库性能，只需要使用select * from v$parameter2即可查看当前的所有参数，如果需要查看特定的参数，只需要执行SELECT name, value FROM v$parameter2 WHERE name IN (xxx）即可。

官方英文解释

V$PARAMETER2 displays information about the initialization parameters that are currently in effect for the session, with each list parameter value appearing as a row in the view. A new session inherits parameter values from the instance-wide values displayed in the V$SYSTEM_PARAMETER2 view.

Presenting the list parameter values in this format enables you to quickly determine the values for a list parameter. For example, if a parameter value is a, b, then the V$PARAMETER view does not tell you if the parameter has two values (both a and b) or one value (a, b). V$PARAMETER2 makes the distinction between the list parameter values clear.

Column	Datatype	Description
`NUM`	`NUMBER`	Parameter number
`NAME`	`VARCHAR2(80)`	Name of the parameter
`TYPE`	`NUMBER`	Parameter type: `1` – Boolean `2` – String `3` – Integer `4` – Parameter file `5` – Reserved `6` – Big integer
`VALUE`	`VARCHAR2(4000)`	Parameter value for the session (if modified within the session); otherwise, the instance-wide parameter value
`DISPLAY_VALUE`	`VARCHAR2(4000)`	Parameter value in a user-friendly format. For example, if the `VALUE` column shows the value `262144` for a big integer parameter, then the `DISPLAY_VALUE` column will show the value `256K`.
`ISDEFAULT`	`VARCHAR2(6)`	Indicates whether the parameter is set to the default value (`TRUE`) or the parameter value was specified in the parameter file (`FALSE`)
`ISSES_MODIFIABLE`	`VARCHAR2(5)`	Indicates whether the parameter can be changed with `ALTER SESSION` (`TRUE`) or not (`FALSE`)
`ISSYS_MODIFIABLE`	`VARCHAR2(9)`	Indicates whether the parameter can be changed with `ALTER SYSTEM` and when the change takes effect: `IMMEDIATE` – Parameter can be changed with `ALTER SYSTEM` regardless of the type of parameter file used to start the instance. The change takes effect immediately. `DEFERRED` – Parameter can be changed with `ALTER SYSTEM` regardless of the type of parameter file used to start the instance. The change takes effect in subsequent sessions. `FALSE` – Parameter cannot be changed with `ALTER SYSTEM` unless a server parameter file was used to start the instance. The change takes effect in subsequent instances.
`ISPDB_MODIFIABLE`	`VARCHAR2(5)`	Indicates whether the parameter can be modified inside a PDB (`TRUE`) or not (`FALSE`). In a non-CDB, the value of this column is `NULL`.
`ISINSTANCE_MODIFIABLE`	`VARCHAR2(5)`	For parameters that can be changed with `ALTER SYSTEM`, indicates whether the value of the parameter can be different for every instance (`TRUE`) or whether the parameter must have the same value for all Real Application Clusters instances (`FALSE`). If the `ISSYS_MODIFIABLE` column is `FALSE`, then this column is always `FALSE`.
`ISMODIFIED`	`VARCHAR2(10)`	Indicates whether the parameter has been modified after instance startup: `MODIFIED` – Parameter has been modified with `ALTER SESSION` `SYSTEM_MOD` – Parameter has been modified with `ALTER SYSTEM` (which causes all the currently logged in sessions’ values to be modified) `FALSE` – Parameter has not been modified after instance startup
`ISADJUSTED`	`VARCHAR2(5)`	Indicates whether Oracle adjusted the input value to a more suitable value (for example, the parameter value should be prime, but the user input a non-prime number, so Oracle adjusted the value to the next prime number)
`ISDEPRECATED`	`VARCHAR2(5)`	Indicates whether the parameter has been deprecated (`TRUE`) or not (`FALSE`)
`ISBASIC`	`VARCHAR2(5)`	Indicates whether the parameter is a basic parameter (`TRUE`) or not (`FALSE`)
`DESCRIPTION`	`VARCHAR2(255)`	Description of the parameter
`ORDINAL`	`NUMBER`	Position (ordinal number) of the parameter value. Useful only for parameters whose values are lists of strings.
`UPDATE_COMMENT`	`VARCHAR2(255)`	Comments associated with the most recent update
`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