Column	Datatype	Description
NUM	NUMBER	Parameter number
NAME	VARCHAR2(64)	Name of the parameter
TYPE	NUMBER	Parameter type: 1 - Boolean 2 - String 3 - Integer 4 - Parameter file 5 - Reserved 6 - Big integer
VALUE	VARCHAR2(512)	Parameter value for the session (if modified within the session); otherwise, the instance-wide parameter value
ISDEFAULT	VARCHAR2(9)	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.
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)
DESCRIPTION	VARCHAR2(64)	Description of the parameter
UPDATE_COMMENT	VARCHAR2(255)	Comments associated with the most recent update

V$PARAMETER2

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.

说明：

1， V$PARAMETER是当前session的初始化参数情况，而V$SYSTEM_PARAMETER则是当前实例范围内的默认的初始化参数。如果当前session内修改了相关的参数，那么V$PARAMETER和V$SYSTEM_PARAMETER中的相应参数值就会不同。V$PARAMETER中的ISMODIFIED字段就会变成MODIFIED（alter session）或者是SYSTEM_MOD（alter system）

2， V$PARAMETER2中的记录基本和V$PARAMETER相同，他们的区别主要在于对含有逗号的多个值的字符的参数的表达方式。举个例子，如果初始化参数中说明数据库有三个控制文件，那么在V$PARAMETER仅会存在一条关于control_files的记录，而在V$PARAMETER2中则会存在三条关于control_files的记录，每条记录标志都表示一个仅仅表示一条控制文件的地址，这三条记录通过ORDINAL来区分。

3，V$SYSTEM_PARAMETER和V$SYSTEM_PARAMETER2之间的关系与V$PARAMETER2和V$PARAMETER相同

V$SPPARAMETER

V$SPPARAMETER displays information about the contents of the server parameter file. If a server parameter file was not used to start the instance, then each row of the view will contain FALSE in the ISSPECIFIED column.