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Re: V$SESSSTAT stat 3 vs V$OPEN_CURSOR

From: Ryan <rgaffuri_at_cox.net>
Date: Thu, 07 Aug 2003 14:54:30 -0800
Message-ID: <F001.005C986E.20030807145430@fatcity.com>


really? I thought v$sesstat was session based statistics?

> I should have known to check Steve's site first (is he still lurking
around
> here?).
>
> One thing I noticed is that one of the cursors listed in V$OPEN_CURSOR is
an
> INSERT into AUD$. This would account for the discrepancy and could match
> the description you provided.
>
> So, in summary, the true number of open cursors is correct in V$SESSTAT
and
> is *not necessarily* the count of rows in the corresponding V$OPEN_CURSOR
> view.
>
> And my apologies to the sticklers of the list who have noticed my
> "V$SESSSTAT" and "V$OPEN_CURSORS"... <sigh>
>
> Rich
>
> Rich Jesse System/Database Administrator
> rjesse_at_qtiworld.com Quad/Tech Inc, Sussex, WI USA
>
>
> > -----Original Message-----
> > From: Tanel Poder [mailto:tanel.poder.003_at_mail.ee]
> > Sent: Thursday, August 07, 2003 4:20 PM
> > To: Multiple recipients of list ORACLE-L
> > Subject: Re: V$SESSSTAT stat 3 vs V$OPEN_CURSOR
> >
> >
> > Hi!
> >
> > This is troubleshooting, not performance tuning ;)
> > As far as Ixora states, v$sesstat "opened cursors current"
> > shows PL/SQL
> > cached cursors as well, even when they are explicitly closed
> > (assuming that
> > session_cached_cursors is set).
> > But v$open_cursor doesn't show the number of cursor
> > structures in UGA, but
> > it shows you (some kind of count) of parse locks which get
> > created in SGA
> > for a SQL statement or PL/SQL block.
> > They provide a link from schema objects to shared SQL area,
> > so the cursors
> > can be invalidated when doing DDL on referenced objects. They
> > are called
> > breakable parse locks in Concepts Manual. As the name says
> > "breakable" -
> > even though you got a lock on schema object, you still can
> > alter it, the
> > lock is just "broken", the cursor is invalidated (but remains
> > cached in UGA)
> > and has to be reloaded on next execution. Here we can have a
> > situation, when
> > as result of DDL, we don't have any breakable parse locks on
> > SGA anymore,
> > but we still have open cursors in UGA. Thus the difference
> > between v$sesstat
> > and v$open_cursor.
> >
> > (this story is based on Concepts manual and Ixora)
> >
> > But for ORA-1000 errors, you should maybe set event for
> > ORA-1000 and dump
> > errorstack. Or sample v$sesstat quite often (once per few
> > seconds), to catch
> > the point where number of open cursors jumps to ceiling (as I
> > understand,
> > it's fairly low normally).
> >
> > And for TAR's - I recommend you to do few Oracle Applications
> > upgrades,
> > especially to fresh versions of major new releases, such
> > 11.5.1 or 2, then
> > you start even seeing severity 1 TARs in your dreams ;)
> >
> > Tanel.
> >
> > ----- Original Message -----
> > To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> > Sent: Thursday, August 07, 2003 11:14 PM
> >
> >
> > > No takers on this from the perf tuning gurus? Please don't
> > make me open a
> > > TAR. Think of the children...
> > >
> > > Rich
> > >
> > > Rich Jesse System/Database Administrator
> > > rjesse_at_qtiworld.com Quad/Tech Inc, Sussex, WI USA
> > >
> > >
> > > > -----Original Message-----
> > > > From: Jesse, Rich
> > > > Sent: Thursday, July 24, 2003 3:39 PM
> > > > To: Multiple recipients of list ORACLE-L
> > > > Subject: V$SESSSTAT stat 3 vs V$OPEN_CURSOR
> > > >
> > > >
> > > > Hey all,
> > > >
> > > > We recently had a problem with a 3rd-party app getting
> > > > "ORA-1000 max open
> > > > cursors exceeded" on their 8.1.7.4 DB. Since OPEN_CURSORS is
> > > > set to 500 in
> > > > the init.ora -- should be more than generous for a tiny app
> > > > on a tiny DB --
> > > > we started looking into how many cursors the app actually has
> > > > open at any
> > > > given time.
> > > >
> > > > While investigating this, I see that the number of rows in
> > > > V$OPEN_CURSORS
> > > > isn't consistent with the value of stat 3 ("opened cursors
> > > > current") of
> > > > V$SESSSTAT. Of the two processes I looked at, each had a
> > > > V$SESSSTAT value
> > > > of "3" for stat 3, while the first had a single entry in
> > > > V$OPEN_CURSOR and
> > > > the second had four.
> > > >
> > > > Should these values match? I looked on Metalink but was
> > > > unable to find any
> > > > reference to the relationship between these, other than a
> > > > forum article
> > > > where the OraSupport person was extraordinarily unhelpful.
> > > >
> > > > TIA,
> > > > Rich
> > > >
> > > > Rich Jesse System/Database Administrator
> > > > rjesse_at_qtiworld.com Quad/Tech Inc, Sussex, WI USA
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Jesse, Rich
> INET: Rich.Jesse_at_qtiworld.com
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Ryan
  INET: rgaffuri_at_cox.net

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Received on Thu Aug 07 2003 - 17:54:30 CDT

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