ok. i've had the following running since lunchtime and will let it run
through the night in hopes that issue occurs again:
@snapper ash,stats,trace 10 999999 lgwr
I will run the following script as well:
#! /bin/bash
while [ 1 ]
do
echo `date` >> /tmp/pstack.26552
pstack 26552 >> /tmp/pstack.26552
echo `date` >> /tmp/pstack.26556
pstack 26556 >> /tmp/pstack.26556
echo `date` >> /tmp/pstack.26560
pstack 26560 >> /tmp/pstack.26560
sleep 5
done
based off:
[oracle@lsst-oradb05 bin]$ ps -ef | egrep "lg.*lsst2db2"
oracle 26552 1 0 Jan17 ? 00:06:14 ora_lgwr_lsst2db2
oracle 26556 1 0 Jan17 ? 00:00:13 ora_lg00_lsst2db2
oracle 26560 1 0 Jan17 ? 00:00:12 ora_lg01_lsst2db2
All sessions for this workload are connecting to service w/ tracing enabled
so we'll have trace data as well.
I will (hopefully) have updates in the morning.
On Tue, Jan 28, 2020 at 4:01 PM Noveljic Nenad <nenad.noveljic@xxxxxxxxxxxx>
wrote:
We need to find out what lg* are doing during long log file sync waits. As
ash samples are entirely missing I propose to sample all lg* processes with
pstack every second and store the information for the later analysis.
Another useful information would be snapper stats output, say, also once
per second and targeted to lg* from the same interval.
This will generate lots of data but you can write a script to periodically
delete it if there weren’t any incidents. You can easily detect them by
counting log file sync samples.
I’m really curious about this as usually long log file sync waits match
some instrumented bg activity which is, apparently, not being the case here.
*Von: *Noveljic Nenad <nenad.noveljic@xxxxxxxxxxxx>
*Datum *Dienstag, 28. Jan. 2020, 10:17 PM
*An: *cary.millsap@xxxxxxxxxxxx <cary.millsap@xxxxxxxxxxxx>, Stefan
Koehler <contact@xxxxxxxx>
*Cc: *Chris Stephens <cstephens16@xxxxxxxxx>, oracle-l <
Oracle-L@xxxxxxxxxxxxx>
*Betreff: *RE: intermittent long "log file sync" waits
In this case, though, there aren’t any ash entries for any of the lg*
processes while the app sessions were waiting in log file sync for a long
time.
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