Re: wrong start_time and start_date in v$transaction

Hi Nenad,

Btw, I've just recalled that we saw twice this year how oracle suddenly stopped without any error messages or core dumps and the last record was something like 'Warning: VKTM detected a time drift'. I'm not sure was it the root cause of it, but just FYI

On Tue, Sep 8, 2020 at 2:33 PM Noveljic Nenad <nenad.noveljic_at_vontobel.com> wrote:

> The dedicated process doesn’t call the timestamp function itself. It
> rather reads the current value from an address location which is
> continuously updated by the VKTM. This is probably an optimization, because
> the real time timestamp function is expensive.
>
>
>
> In my case, vktm hangs and it doesn’t update the location holding the
> current Epoch time. The stale timestamp gets then copied in each
> transaction entry.
>
>
>
> Since vktm hangs in nanosleep OS kernel call, it might be an OS issue:
>
>
>
> pstack 14583
>
> 14583: ora_vktm_ATRM2
>
> 00007fff93c76eba nanosleep (7fffbfffc7d0, 7fffbfffc7e0)
>
> 00000000072f3e9a sltrusleep () + 6a
>
> 000000000758b994 kstmrmtickcntkeeper () + 5a4
>
> 000000000758b1f4 kstmmainvktm () + 194
>
> 00000000072f5869 ksbrdp () + 9a9
>
> 0000000006efc489 opirip () + 2b9
>
> 0000000006118950 opidrv () + 160
>
> 0000000006118767 sou2o () + 97
>
> 0000000006118534 opimai_real () + a4
>
> 000000000611808b ssthrdmain () + 26b
>
> 0000000006117df9 main () + a9
>
> 0000000007771e34 ???????? ()
>
>
>
> Best regards,
>
>
>
> Nenad
>
>
>
> https://nenadnoveljic.com/blog
>
>
>
>
>
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-- 
Best regards,
Sayan Malakshinov
Oracle performance tuning engineer
Oracle ACE Associate
http://orasql.org

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