Re: Why dba_hist_waitclassmet_history has 0 line?

Thanks for exploring those views you mentioned previously, Kyle 😊.

But they're not empty data for those views marking ALERT by you. Maybe really breached some limit (it doesn't seem like to exceed how much lines).

Best Regards
Quanwen Zhao

在 2021年12月3日星期五，kyle Hailey <kylelf_at_gmail.com> 写道：
>
> Yeah, I recall empty dba_hist_waitclassmet_history being confusing.
> I believe dba_hist_waitclassmet_history is just for alerting entries when
some limit has been breached.
> It's been a long time since I've looked at this stuff.
>
> Statistics
>
> DBA_HIST_SYSMETRIC_SUMMARY – max, min, avg standard deviation
> DBA_HIST_SYSSTAT (cumulative)
> DBA_HIST_SYSMETRIC_HISTORY (alerts)
>
> Waits
>
> WAITCLASSMETRIC_HISTORY (alerts)
> DBA_HIST_SYSTEM_EVENT (cumulative)
>
> File IO
>
> DBA_HIST_FILEMETRIC_HISTORY (alerts)
> DBA_HIST_FILESTATXS (cumulative)
>
> On Sun, Nov 28, 2021 at 12:49 AM Quanwen Zhao <quanwenzhao_at_gmail.com>
wrote:
>>
>> Hello Listeners 😊,
>> Recently I've found three important views about "v$waitclassmetric",
"v$waitclassmetric_history", and "dba_hist_waitclassmet_history". Here're the corresponding links from oracle online docs:
>>

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
>>
>> Quoted the brief introduction for themselves:
>>>
>>> 9.131 V$WAITCLASSMETRIC
>>>
>>> V$WAITCLASSMETRIC displays metric values of wait classes for the most
recent 60-second interval. A history of the last one hour will be kept in the system.
>>
>>
>>>
>>> 9.132 V$WAITCLASSMETRIC_HISTORY
>>>
>>> V$WAITCLASSMETRIC_HISTORY displays metric values of wait classes for
all intervals in the last one hour.
>>>
>>> The columns for V$WAITCLASSMETRIC_HISTORY are the same as those
for V$WAITCLASSMETRIC.
>>>
>>> 5.84 DBA_HIST_WAITCLASSMET_HISTORY
>>>
>>> DBA_HIST_WAITCLASSMET_HISTORY displays the history of the wait event
class metric data kept by the Workload Repository.
>>
>> But why dba_hist_waitclassmet_history has 0 line? Here's my query from
oracle 21.3 (test db) and found all the same situation from 19.3 and 11.2.0.4:
>>>
>>> 16:43:23 SYS_at_ORACDB> select count(*) from v$waitclassmetric;
>>>
>>> COUNT(*)
>>> ----------
>>> 13
>>>
>>> 16:43:29 SYS_at_ORACDB> select count(*) from v$waitclassmetric_history;
>>>
>>> COUNT(*)
>>> ----------
>>> 793
>>>
>>> 16:43:33 SYS_at_ORACDB> select count(*) from dba_hist_waitclassmet_history;
>>>
>>> COUNT(*)
>>> ----------
>>> 0
>>
>> Has anybody else encountered it? Oracle hasn't saved the historical
wait class metric to view dba_hist_waitclassmet_history or is it a bug?
>> Best Regards
>> Quanwen Zhao

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