V$SESSION

WAIT_TIME

NUMBER

If the session is currently waiting, then the value is 
0
. If the session is not in a wait, then the value is as follows:

> 
0
 - Value is the duration of the last wait in hundredths of a second

-1
 - Duration of the last wait was less than a hundredth of a second

-2
 - Parameter 
TIMED_STATISTICS
 was set to 
false

This column has been deprecated in favor of the columns 
WAIT_TIME_MICRO
 and 
STATE
.

1.當會話的state為waiting時，wait_time為0.

2.wait_time 大於0時，指的是從上一次waiting到當前非waiting狀態的間隔時間，單位為1/100秒。

3.wait_time為-1時，指的是從上一次waiting到當前非waiting狀態的間隔時間小於1/100秒。

4.wait_time為-2時，TIMED_STATISTICS 設成了fasle。

V$ACTIVE_SESSION_HISTORY

WAIT_TIME

NUMBER

0
 if the session was waiting at the time of sampling

Total wait time for the event for which the session last waited if the session was on the CPU when sampled

Whether or not 
WAIT_TIME
 = 
0
 is what is useful to find the 
SESSION_STATE
 at the time of sampling, rather than the actual value of 
WAIT_TIME
 itself. 
Maps to V$SESSION.WAIT_TIME
.

1.wait_time為0 ，當在取樣時，會話狀態是waiting。

2.wait_time大於0,當在取樣時，會話狀態是on cpu，這個值便是從往上最後一次狀態為waitting到當前的時間區間。

3.這裡的取樣頻率是1s.

DBA_HIST_ACTIVE_SESS_HISTORY

WAIT_TIME

NUMBER

Total wait time (in microseconds) for the event for which the session last waited (
0
 if currently waiting)

1.wait_time為0 ，當在取樣時，會話狀態是waiting。

2.wait_time大於0,當在取樣時，會話狀態是on cpu，這個值便是從往上最後一次狀態為waitting到當前的時間區間。

3.這裡的取樣頻率是10s.

session檢視中wait_time

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