Thanks, Jonathan!
Your ideas is very good! Perhaps I might also found the related DDL info
from dbms_metadata.get_ddl().
I need clarify why I go to check dba_hist_waitclassmet_history - I wanna
check Avtive Sessions Per Wait Class from EMCC 13.5 in the last 24 hours
and more old days (7 or 31 days).
Yes, I can get several data from v$waitclassmetric_history (in the last 60
minutes) and v$waitclassmetric (in the last 1 minute).
I guess Oracle might suggest we go to check dba_hist_active_sess_history if
elapsed time is more than 1 hour. Because I've also noticed that I can see
the historical graph of ASH analysis when clicking the each legend (such
as, cpu_used or cpu_wait) from the graph (Active Sessions Per Wait Class)
of EMCC 13.5.
Best Regards
Quanwen Zhao
在 2021年12月3日星期五,Jonathan Lewis <jlewisoracle@xxxxxxxxx> 写道:
parameter (or call to an internal package) that changes the way Oracle
It must be a deliberate coding decision, and there may be a hidden
Regards"v$waitclassmetric_history", and "dba_hist_waitclassmet_history". Here're
Jonathan Lewis
On Sun, 28 Nov 2021 at 08:49, Quanwen Zhao <quanwenzhao@xxxxxxxxx> wrote:
Hello Listeners 😊,
Recently I've found three important views about "v$waitclassmetric",
https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/V-WAITCLASSMETRIC.html
https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/V-WAITCLASSMETRIC_HISTORY.html#GUID-854BB495-19FC-4EB4-A81C-4D0EEA13B83C
https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/DBA_HIST_WAITCLASSMET_HISTORY.html#GUID-A931DFBF-4023-41F0-A333-E56741DE589D
recent 60-second interval. A history of the last one hour will be kept in
Quoted the brief introduction for themselves:
9.131 V$WAITCLASSMETRIC
V$WAITCLASSMETRIC displays metric values of wait classes for the most
all intervals in the last one hour.
9.132 V$WAITCLASSMETRIC_HISTORY
V$WAITCLASSMETRIC_HISTORY displays metric values of wait classes for
for V$WAITCLASSMETRIC.
The columns for V$WAITCLASSMETRIC_HISTORY are the same as those
class metric data kept by the Workload Repository.
5.84 DBA_HIST_WAITCLASSMET_HISTORY
DBA_HIST_WAITCLASSMET_HISTORY displays the history of the wait event
oracle 21.3 (test db) and found all the same situation from 19.3 and
But why dba_hist_waitclassmet_history has 0 line? Here's my query from
wait class metric to view dba_hist_waitclassmet_history or is it a bug?
16:43:23 SYS@ORACDB> select count(*) from v$waitclassmetric;
COUNT(*)
----------
13
16:43:29 SYS@ORACDB> select count(*) from v$waitclassmetric_history;
COUNT(*)
----------
793
16:43:33 SYS@ORACDB> select count(*) from dba_hist_waitclassmet_history;
COUNT(*)
----------
0
Has anybody else encountered it? Oracle hasn't saved the historical
Best Regards
Quanwen Zhao