Re: reads by KTSJ

Hi Nenad!Both Wnnnn and KTSJ slaves are space management processes. Heuristically, I would check whether there is a shortage of space in any of your tablespaces. Other than that, you can try tracing Wnnnn process or KTSJ slave processes using oradebug event. 10046 trace files may give you better insight in what is going on.Regards

On Tue, 2020-05-12 at 21:02 +0000, Noveljic Nenad wrote:
> I started occasionally seeing KTSJ slaves heavily waiting on “free
> buffer waits” and “db file sequential read” after upgrading from
> 18.7.0.0.190716 to 19.7.0.0.200414:
>
> SQL> _at_ash_wait_chains2 "program2||' '||event2||' '||module||'
> '||action" "program2 like '(W%'" "to_date('2020-05-12 13:37:15')"
> "to_date('2020-05-12 14:37:15')"
>
> -- Display ASH Wait Chain Signatures script v0.5 BETA by Tanel Poder
> (
> http://blog.tanelpoder.com )
>
> %This SECONDS AAS WAIT_CHAIN
>
>
>
> FIRST_SEEN
>
> LAST_SEEN
> ------ ---------- ------- -----------------------------------------
> -------------------------------------------------------------------
> -------------------------------------------------------------------
> -------------------------------------------------------------------
> ----------------------------------------------------------
> ------------------- -------------------
> 22% 310 .1 -> (Wnnn) free buffer waits KTSJ KTSJ
> Slave -> (DBWnnn) db file parallel write
>
>
>
> 2020-05-12
> 13:46:55 2020-05-12 13:48:40
> 10% 144 .0 -> (Wnnn) db file sequential read KTSJ
> KTSJ
> Slave
>
>
>
> 2020-05-12 13:46:54 2020-05-12 13:48:52
> 10% 144 .0 -> (WnnA) free buffer waits KTSJ KTSJ
> Slave -> (DBWnnn) db file parallel
> write
>
>
> 2020-05-12
> 13:46:55 2020-05-12 13:57:13
> 7% 104 .0 -> (WnnA) db file sequential read KTSJ
> KTSJ
> Slave
>
>
>
> 2020-05-12 13:46:54 2020-05-12
> 13:57:11
>
> Some of the affected processes have the following entries in the
> trace file:
>
> *** SESSION ID:(1202.8580) 2020-05-12T13:46:54.295884+02:00
> *** CLIENT ID:() 2020-05-12T13:46:54.295916+02:00
> *** SERVICE NAME:(SYS$BACKGROUND) 2020-05-12T13:46:54.295947+02:00
> *** MODULE NAME:(KTSJ) 2020-05-12T13:46:54.295978+02:00
> *** ACTION NAME:(KTSJ Slave) 2020-05-12T13:46:54.296009+02:00
> *** CLIENT DRIVER:() 2020-05-12T13:46:54.296039+02:00
>
> [ktspsc_segmon] submitted segfix task
> [ktspsc_segmon] submitted segfix task
> [ktspsc_segmon] submitted segfix task
>
>
> The tablespaces are autoextensible, but I don’t know if they were
> extended during this time period. The IO performance is OK.
>
> I examined one of the read bloccks – it belongs to a user schema,
> nothing special about it:
>
> How to figure out what might have caused this KTSJ slave activity?
>
> Best regards,
>
> Nenad
>
> https://nenadnoveljic.com/blog/
>
>
>
>
>
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-- 
Mladen GogalaDatabase ConsultantTel: (347) 321-1217Email:gogala.mladen_at_gmail.com


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