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> @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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