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session：实时vactive_session_history ：每1秒将v
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session中记录保存到 v
session中记录保存到vactive_session_history 视图中，只会加载非idle会话。存在内存，重启就会消失。用做ASH报表。 _ash_sampling_interval
dba_hist_active_sess_history：每隔10秒钟转储来自v$active_session_history的活动session信息。 _ash_disk_filter_ratio
V$SESSION
V$SESSION displays session information for each current session.
V$ACTIVE_SESSION_HISTORY
V$ACTIVE_SESSION_HISTORY displays sampled session activity in the database.
It contains snapshots of active database sessions taken once a second. A database session is considered active if it was on the CPU or was waiting for an event that didn’t belong to the Idle wait class. Refer to the V$EVENT_NAME view for more information on wait classes.
This view contains one row for each active session per sample and returns the latest session sample rows first. A majority of the columns describing the session in the active session history are present in the V$SESSION view.
DBA_HIST_ACTIVE_SESS_HISTORY
DBA_HIST_ACTIVE_SESS_HISTORY displays the history of the contents of the in-memory active session history of recent system activity.
DBA_HIST_ACTIVE_SESS_HISTORY contains snapshots of V A C T I V E S E S S I O N H I S T O R Y . S e e " V ACTIVE_SESSION_HISTORY. See "V ACTIVES?ESSIONH?ISTORY.See"VACTIVE_SESSION_HISTORY" for further interpretation details for many of these columns (except SNAP_ID, DBID, and INSTANCE_NUMBER).
