通过 v$parameter 视图看参数修改级别(11g, 18c, 19c)

V$PARAMETER displays information about the initialization parameters that are currently in effect for the session. A new session inherits parameter values from the instance-wide values displayed by the
V$SYSTEM_PARAMETER view.

1. ISDEFAULT 是否是默认值
Indicates whether the parameter is set to the default value (TRUE) or the parameter value was specified in the parameter file (FALSE)

2. ISSES_MODIFIABLE 是否可在 SESSION 级别修改
Indicates whether the parameter can be changed with ALTER SESSION (TRUE) or not (FALSE)

3. ISSYS_MODIFIABLE 是否可以在 SYSTEM 级别修改
Indicates whether the parameter can be changed with ALTER SYSTEM and when the change takes effect:
    # 立即对所有 SESSION 生效
    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.

    # 对修改完成之后建立的 SESSION 生效
    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.

    # 需重启实例才能生效
    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.

4. ISINSTANCE_MODIFIABLE 集群的不同节点是否可以设置不同的参数值
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.

5. ISMODIFIED 参数是否被修改过以及修改的级别
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

6. ISADJUSTED
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)

7. ISDEPRECATED
Indicates whether the parameter has been deprecated (TRUE) or not (FALSE)

8. ISBASIC
Indicates whether the parameter is a basic parameter (TRUE) or not (FALSE)

18C 新增参数
9. CON_ID 容器 ID
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

19C 新增参数
10. ISPDB_MODIFIABLE 是否可在 PDB 级别修改
Indicates whether the parameter can be modified inside a PDB (TRUE) or not (FALSE)