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Re: Number of threads is twice the number of sessions with 10.2 on Windows platform

From: Paolo Desalvo <>
Date: Fri, 24 Feb 2006 09:29:39 -0500
Message-ID: <>

Hi all,

I'm glad that so many people can reproduce that, I've also opened a TAR with Oracle Support but they say they can't reproduce it.

Anyway, I know that enabling DCD will fire a watchdog thread in previous release (10.1 backward) but in my test DCD is disabled, and Giovanni's test confirm it.

Maybe there's something wrong with the DCD and the watchdog thread is fired whatever the sqlnet.expire_time is set.

But the most important point is: how much virtual memory are consuming those additional threads?
What are they doing, if something?
On a 32bit Windows box, with a 2GB limit of addressable memory, we can have no more than 170-180 users connected before the VM reaches 2GB, so I'm wondering how much VM those threads are eating.

I will try to figure out with more tests today but I don't have any MS Development Suite (Visual something) that could identify and measure the threads of ORACLE.EXE.

I'll post any reasonable information coming from Oracle Support. Thanks to everyone, I appreciated all suggestions.


> Hi all,
> more little tests on the issue. I knew that enabling the parameter
> sqlnet.expire_time (i.e. setting it to a value more than 0) has this
> side effect, i.e. it creates another thread (a watchdog thread) only
> for monitoring the real one. I just tested this on a 9.2 on winzozz.
> Now my opinion is that in 10.2 there is the watchdog thread even if
> sqlnet.expire time is 0. I enabled the sqlnet trace with expire_time=0
> and the log clearly reports DCD disabled.I enalbed DCD with
> expire_time=1, the sqlnet log reports the dcd enabled, but the number
> of threads created is "still" two.
> Now these tests are not enough to build a theory on what's happening
> but my guess is that starting from 10.X there is an watchdog thread
> with monitors the real session. Time permitting I will do some others
> test to verify if dead session detecting is changed from 9.2. to 10.2
> and how.
> Hope it helps,
> Giovanni
> On 2/23/06, Paolo Desalvo <> wrote:
>> Hi all.
>> I have noticed too many threads in the Task Manager related to the
>> ORACLE.EXE process for 10.2.
>> So I run a simple testcase program on a test server with no activity
>> and I fired 10 SQLPLUS connections to the 10.2 database; the number of
>> threads increased from 31 to 51, so 2 threads for each session connected
>> to the
>> database.
>> Then I run the same program on the same test server directing the
>> connections to a 9.2 database; the number of threads increased from 12
>> to 22, so 1
>> thread for each session, as expected.
>> Is there anybody with the same problem?
>> Thanks
>> Paolo
>> --
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Received on Fri Feb 24 2006 - 08:29:39 CST

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