Re: High response time with top 'Other' and 'application' wait class

Hi!

"gcs drm freeze in enter server mode" is specific to RAC. It seems to be triggered by instance leaving or joining the cluster. Brownouts during dynamic remastering is expected behaviour.

On Tue, 29 Nov 2022, 03:56 Lok P, <loknath.73_at_gmail.com> wrote:

> Hello ,
> It's version 19C of the oracle database. We got complaints from the
> application team of sudden slowness and thus app traffic automatically
> redirected to another active DB replica.While looking into the DB side, we
> do observe high wait events from wait class 'Other' and 'Application' in
> OEM. It lasted for exactly 2-3 minutes as the application team is
> complaining about. And then fetching the "ash wait chain" and "ash top" ,
> it's pointing to significantly high wait event like "reliable message"
> (~75%), "enq: KO - fast object checkpoint","gcs drm freeze in enter server
> mode" from same wait class 'other' and 'application'.
>
> Below is the ASH top and ASH wait chain from the issue duration of
> ~5minutes interval. And the select query which is coming on top. And table
> CB is holding just ~41 rows in it.
> https://gist.github.com/oraclelearner/44394ab8206fc7bd51041eb3d45bdf9f
>
> And also the top query which is showing in "ash top" is a SELECT query and
> it does have a FTS in it (which is suggesting why the checkpoint waits),
> however, this select query doesn't have any plan change observed in it or
> not any high execution. And also we are not seeing any specific blocking
> session for this. The "wait chain" showing LMON/lock monitor process in one
> of the lines also does point to some event like "Wait for msg sends to
> complete ''. Not yet able to figure out how these are related to this
> issue. Still trying to understand what could have caused such a scenario?
>
> This SELECT query executes 100's of thousands of times in ~15minutes
> window. So is it possible that this query(or say its underlying table CB)
> might have thrashed out from buffer cache to disk and fetched data from
> disk rather than cache for that time and this causing all these sort of
> issues? And considering this table is very small (~1MB in size and holding
> just ~41 rows), should we consider putting it as inmemory by changing
> "inmemory_clause_default" to 'BASE_LEVEL' and "INMEMORY_SIZE" to 16GB ?
>
>

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