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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Redo latch contention
Any description of x$trace? In the docs ?.
Alex Hillman
-----Original Message-----
Sent: Saturday, June 16, 2001 5:35 PM
To: Multiple recipients of list ORACLE-L
Or with Cary Millsap's hprof/Sparky stuff (hotsos.com). I'm deligthed that
guys like
you and Cary are writing tools/products that harvest the enormous amount of
useful
stuff available in 10046 level 8/12 trace files.
You know what would be really cool? The same stuff is available via x$trace.
x$trace
is in itself much more non-intrusive than 10046 traces (it uses memory
buffers), but
has some features and possibilities that sets it apart:
So it would be really cool if some tool some day could get some of this data out :).
"Danisment Gazi Unal (Unal Bilisim)" wrote:
> Mogens,
>
> You are right.
>
> nothing is a performance problem unless there is a time contention.
>
> In general, it's very hard to see time spent in each latch. itrprof SQL
Analyzer
> with waitgroup=(name,P1,P2) can report time spent in each latch. So, you
can see
> time spent in A latch, time spent in B latch, etc. I'm not a very old dba,
but I
> don't think many latches can be tuned by init.ora parameters.
>
> with waitgroup=(name,P1), you can see time spent in each enqueue such as 5
sec
> in (TX), 3 sec in (TM) etc.
>
> 'latch free' and 'enqueue' waits do not make sense themselves. You can
> drill-down these each waits by itrprof.
>
> a little marketing...
>
> Mogens Nørgaard wrote:
>
> > First of all, if you don't see cumulated waits for the 'latch free'
event in
> > either v$system_event or v$session_event (for a specific session/job)
there
> > is absolutely no need to do anything about these ratios. It's about the
only
> > two latches mentioned in the reference books and it's about the only two
> > latches that never really have a problem :).
> >
> > My guess is that this effort (increasing log_simultaneous_copies and
> > log_small_entry_max_size) hasn't increased performance on your system
> > whatsoever.
> >
> > If - only if - you have latch contention/waits in the system (high
> > percentage of time_waited in the above-mentioned
> > v$system_event/v$session_event, you should ignore all those calculations
> > with gets and misses and insted just look in v$latch like this:
> >
> > select name, sleeps from v$latch order by 2;
> >
> > to find the latches with highest contention. But again: If your system
or
> > session is not really waiting for latches, why bother?
> >
> > Rajesh Dayal wrote:
> >
> > > Hi All,
> > > I had some situation of Redo Allocation and copy latch
> > > contention as stated in following output.....
> > >
> > > SQL> SELECT substr(NAME,1,18) NAME, GETS,MISSES, IMMEDIATE_GETS,
> > > IMMEDIATE_MISSES
> > > FROM V$LATCH WHERE NAME LIKE '%redo%'
> > > /
> > >
> > > NAME GETS MISSES IMMEDIATE_GETS
IMMEDIATE_MISSES
> > >
> > > ------------------ ---------- ---------- --------------
-- Venlig hilsen Mogens Nørgaard Technical Director Miracle A/S, Denmark Web: http://MiracleAS.dk Mobile: +45 2527 7100 -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Mogens =?iso-8859-1?Q?N=F8rgaard?= INET: mno_at_MiracleAS.dk Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Hillman, Alex INET: Alex.Hillman_at_usmint.treas.gov Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Mon Jun 18 2001 - 09:04:37 CDT
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