System and session state

系统级的：

Session级的

event的视图(session级别2个、系统级别一个)：

SELECT *FROM v$session_event;

SELECT *FROM v$session_wait;

SELECT *FROM v$system_event;

重要参数：

statistics_level basic typical all

timed_statistics true false

timed_os_statistics 0

db_keep_cache_size 0