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RE: Missing time in 10046 trace file

From: Cary Millsap <>
Date: Fri, 1 Oct 2004 11:46:18 -0500
Message-ID: <00a101c4a7d6$2c6234d0$6900a8c0@CVMLAP02>

This is why I so hate the term "wait"...

The ela value of a 'latch free' timed event is the duration of a = sleep-like
OS call. You're referring to the quantity D in the following relation:

        D =3D e[dbcall] - (c[dbcall] + sum(ela[dbcall]))

The large D value that you describe is probably the result of process preemption (as John has suggested).

An Oracle kernel process consumes a lot of CPU before it ever gets to = the
point at which it will execute the 'latch free' timed event. If a lot of kernel processes are fighting for the same small set of latches, then = there
will be a lot of CPU capacity wasted, and in severe cases you'll see = lots of
time spent preempted. ...Which is, I believe, exactly what you're = seeing.

Read "Why you should focus on LIOs instead of PIOs" at = for
the gory details.

Cary Millsap
Hotsos Enterprises, Ltd.
* Nullius in verba *

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-----Original Message-----
From: =
On Behalf Of John Kanagaraj
Sent: Thursday, September 30, 2004 5:54 PM To: ''; Oracle-L
Subject: RE: Missing time in 10046 trace file


>tim value of the FETCH 2276365740 from the time value of the EXEC
>2276356674 I get approx 90 seconds (9066 centi-secs) which is nowhere
>close to adding all the ela's of the waits (48 centi-secs). Am I
>looking at what they call unmeasured/unaccounted-for time?

Note that latches can 'sleep' and while they are sleeping, this time = isn't
counted under 'waiting'. This sleep is successivley for longer = periods... I
think Steve Adams discussed this very clearly in his book. If you look = at
Statspack snapshots between these periods, you might see more than usual values under the SLEEP[n] columns. And yes, when CPU thrashing occurs, = the
unaccounted time increases as the context switching times are not = counted
within Oracle....

John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)

Listen to great, commercial-free christian music 24x7x365 at

Received on Fri Oct 01 2004 - 11:43:21 CDT

Original text of this message