Active Session History

Oracle Database 10g has upgraded its v$session view to include wait events and their durations. However, this view has the values in real time and does not keep track of information to be viewed later. Active Session History (ASH), is very much like AWR, and stores the session performance statistics in a buffer for analysis later. Unlike AWR storage in a table, ASH storage is in memory viewable from v$active_session_history. The data on active sessions is polled every second and the older entries are removed from memory to accommodate the latest ones in a circular manner.

The following query is an example of how to get session information along with time waited on events:

select session_id||' - '||session_serial# SID, v$event_name.name, wait_time, time_waited
from v$active_session_history , v$event_name
SEE CODE DEPOT FOR FULL SCRIPT

The above script provides the name of the event and time spent in waiting.  A sample portion of the lengthy output is as follows: