V$MYSTAT、V$SESSTAT、V$SYSSTAT、V$STATNAME

官方解釋：

V$MYSTAT

V$MYSTAT contains statistics on the current session.

Column	Datatype	Description
SID	NUMBER	ID of the current session
STATISTIC#	NUMBER	Number of the statistic
VALUE	NUMBER	Value of the statistic

V$MYSTAT視圖存放了當前會話的一些統計信息， 一般會用該視圖查看當前會話的ID，也就是SID列；

該視圖和另外三個視圖有關聯性：V$SESSTAT 、V$SYSSTAT、V$STATNAME

V$SESSTAT

V$SESSTAT displays user session statistics. To find the name of the statistic associated with each statistic number (STATISTIC#), query the V$STATNAME view.

Column	Datatype	Description
SID	NUMBER	Session identifier
STATISTIC#	NUMBER	Statistic number Note: Statistics numbers are not guaranteed to remain constant from one release to another. Therefore, you should rely on the statistics name rather than its number in your applications.
VALUE	NUMBER	Statistic value

該視圖顯示所有會話的統計

V$SYSSTAT

V$SYSSTAT displays system statistics. To find the name of the statistic associated with each statistic number (STATISTIC#), query the V$STATNAME view.

Column	Datatype	Description
STATISTIC#	NUMBER	Statistic number Note: Statistics numbers are not guaranteed to remain constant from one release to another. Therefore, you should rely on the statistics name rather than its number in your applications.
NAME	VARCHAR2(64)	Statistic name. You can get a complete listing of statistic names by querying the V$STATNAMEview.
CLASS	NUMBER	A number representing one or more statistics class. The following class numbers are additive: 1 - User 2 - Redo 4 - Enqueue 8 - Cache 16 - OS 32 - Real Application Clusters 64 - SQL 128 - Debug
VALUE	NUMBER	Statistic value
STAT_ID	NUMBER	Identifier of the statistic

該視圖顯示系統的一些統計

V$STATNAME

V$STATNAME displays decoded statistic names for the statistics shown in the V$SESSTAT and V$SYSSTAT tables.

On some platforms, the NAME and CLASS columns contain additional operating system-specific statistics.

Column	Datatype	Description
STATISTIC#	NUMBER	Statistic number Note: Statistics numbers are not guaranteed to remain constant from one release to another. Therefore, you should rely on the statistics name rather than its number in your applications.
NAME	VARCHAR2(64)	Statistic name
CLASS	NUMBER	A number representing one or more statistics classes. The following class numbers are additive: 1 - User 2 - Redo 4 - Enqueue 8 - Cache 16 - OS 32 - Real Application Clusters 64 - SQL 128 - Debug
STAT_ID	NUMBER	Identifier of the statistic

該視圖存放了一個STATISTIC# 所對應的名稱列表，上面三個視圖都可以用STATISTIC# 這一列關聯取出相應的名稱；