时间：2021-07-01 10:21:17 帮助过：19人阅读
V$SYSTEM_EVENT V$SYSTEM_EVENT displaysinformation on total waits for an event. Note thatthe TIME_WAITED and AVERAGE_WAIT columnswill contain a value of zero on those platforms that do not supporta fast timing mechanism. If you are running
V$SYSTEM_EVENT TIME_WAITED AVERAGE_WAIT TIMED_STATISTICS TRUE
See Also:
"TIMED_STATISTICS"
| Column | Datatype | Description |
|---|---|---|
EVENT |
VARCHAR2(64) |
Name of the wait event |
TOTAL_WAITS |
NUMBER |
Total number of waits for the event |
TOTAL_TIMEOUTS |
NUMBER |
Total number of timeouts for the event |
TIME_WAITED |
NUMBER |
Total amount of time waited for the event(in hundredths of a second) |
AVERAGE_WAIT |
NUMBER |
Average amount of time waited for the event(in hundredths of a second) |
TIME_WAITED_MICRO |
NUMBER |
Total amount of time waited for the event(in microseconds) |
TOTAL_WAITS_FG |
NUMBER |
Total number of waits for the event, fromforeground sessions |
TOTAL_TIMEOUTS_FG |
NUMBER |
Total number of timeouts for the event, fromforeground sessions |
TIME_WAITED_FG |
NUMBER |
Amount of time waited for the event (inhundredths of a second), from foreground sessions |
AVERAGE_WAIT_FG |
NUMBER |
Average amount of time waited for the event(in hundredths of a second), from foreground sessions |
TIME_WAITED_MICRO_FG |
NUMBER |
Amount of time waited for the event (inmicroseconds), from foreground sessions |
EVENT_ID |
NUMBER |
Identifier of the wait event |
WAIT_CLASS_ID |
NUMBER |
Identifier of the class of the waitevent |
WAIT_CLASS# |
NUMBER |
Number of the class of the wait event |
WAIT_CLASS |
VARCHAR2(64) |
Name of the class of the wait event |
本视图概括了实例各项事件的等待信息。v$session_wait显示了系统的当前等待项，v$system_event则提供了自实例启动后各个等待事件的概括。常用于获取系统等待信息的历史影象。而通过两个snapshot获取等待项增量，则可以确定这段时间内系统的等待项。
V$SYSTEM_EVENT中的常用列
l
l
l
l
l
注释：
存在等待（某事），就可能会产生等待的该事没来，即所谓等待超时。
示例：
1.查看系统的各项等待，按总耗时排序
SELECT event,total_waits waits,total_timeouts timeouts,
FROM V$SYSTEM_EVENT
ORDER BY 4 DESC;
比如，通过checkpoint completed、log file switch（checkpointincomplete）可以查看检查点进程的性能。通过log file parallel write、log file switchcompleted可以查看联机重做日志文件的性能。通过log file switch（archivingneeded）事件可以检查归档进程的性能。
找出瓶颈：
1。通过Statspack列出空闲事件。
2。检查不同事件的等待时间开销。
3。检查每条等待记录的平均用时，因为某些等待事件(比较log file switchcompletion)可能周期性地发生，但发生时却造成了严重的性能损耗。