Re: V$active session history
- From: Dragutin Jastrebic <orahawk@xxxxxxxxx>
- To: tanel@xxxxxxxxxxxxxx
- Date: Thu, 26 Mar 2015 07:36:21 +0100
2015-03-26 7:31 GMT+01:00 Dragutin Jastrebic <orahawk@xxxxxxxxx>:
> =>
> V$ session is actually the ultimate source of session performance
> information (there's no such thing a "refreshing" v$session) as each
> session directly and immediately updates what they've up to right in the
> session state object (that's externalized in v$session). There are a few
> fields in the session state object that don't get externalized by the v$
> and since 11g a special place called AshLoc where sessions continuously
> update on which execution plan line the SQL execution happens to be.
> <=
>
>
> This behaviour of v$session can sometimes even be misleading to the DBA,
> in the case
> of the short database polling queries (keepalive)
>
>
> I remember the situation , (couple of years of ago and with Oracle 10g) ,
> I was looking for a problematic query that the client module was
> executing.
>
> I have started with v$session but every time I have queried it, I could
> not find anything but the idle sessions with "SQL*NET from client" as the
> waiting event.
> But of course the look at v$sql.executions field value that was constantly
> progressing , confirmed that this short query was indeed executing.
> And v$active_session_history confirmed it as well.
>
> Dragutin
>
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