RE: wrong start_time and start_date in v$transaction

From: Noveljic Nenad <nenad.noveljic_at_vontobel.com>
Date: Tue, 1 Sep 2020 11:32:35 +0000
Message-ID: <23642_1598959975_5F4E3167_23642_7579_1_6f126e9caab14ea68199a52dbce868f6_at_vontobel.com>



Jonathan,
Sayan,
Andy,

"Doesn't change" - depends on the power of 10 in the (hypothetical) error and the amount of time Nenad watched (maybe the time stamp increases by one second every 20 minutes, or every 200 minutes).

>start_time & start_date haven't changed within 24 hours.

Anything in any of the alert logs about processes not starting up properly, or using some specific function that doesn't get mentioned in other alert logs?

>The only startup error message is:

ORA-00800: soft external error, arguments: [Set Priority Failed], [VKTM], [Check traces and OS configuration], [Check Oracle document and MOS notes], [] Incident details in: /u00/oracle/orabase/diag/rdbms/acsi3_site1/ACSI3/incident/incdir_129660/ACSI3_vktm_9138_i129660.trc

Are any of the funny instances running on virtual machines ?
>Everything is running on Solaris containers. However, only a minority of the databases is being affected.

I recall a case where running on vmware some processes would intermittently record a "tim=" value in a trace file that was millions of centiseconds wrong.

>Tim in the SQL trace is correct:

>..tim=11591151275421

>get_t_hr0

1587367589894044

>python convert_tim_to_localtime.py 11591151275421 1587367589894044
2020-09-01 13:12:21.169465

>(The programs above are from https://nenadnoveljic.com/blog/high-resolution-time-human-readable/)

Is there something like faketime, libfaketime, strange LD_PRELOAD?

>Nothing strange.

pargs -e 24032 | grep -i fake
pargs -e 24032 | grep -i LD
envp[17]: LD_LIBRARY_PATH=/u00/oracle/orabase/product/18.7.0.0.190716_a/lib

>Besides that, sysdate returns the correct value.
But thanks for the link - I didn't know about this!

Are the instances that have the problem connected by DB links?
>No.

What about the others?
>Some do have links some don't.

Do you have similar wrongness with scn_to_timestamp?
>No.

SQL> select first_time,first_change# from v$log ;

>FIRST_TIME FIRST_CHANGE#

------------------- -------------
...01.09.2020 02:12:54      12374018

>SQL> select scn_to_timestamp(12374018) from dual ;

>SCN_TO_TIMESTAMP(12374018)



01-SEP-20 02.12.54.000000000 AM
>Can you replicate with a fresh instance using the same oracle home?
No

Thanks,
Nenad

https://nenadnoveljic.com/blog/



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Received on Tue Sep 01 2020 - 13:32:35 CEST

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