RE: How to make a session active with wait event of 'sql*net message FROM client'?

From: Bobak, Mark <Mark.Bobak_at_proquest.com>
Date: Wed, 17 Jun 2009 19:13:37 -0400
Message-ID: <6AFC12B9BFCDEA45B7274C534738067F1857ED3F_at_AAPQMAILBX02V.proque.st>

Hmm...I just went to a moderately busy database and had no problems finding such sessions: SQL> l
  1* select count(*) From v$session where status='ACTIVE' and event = 'SQL*Net message from client' SQL> /   COUNT(*)

---

         9

1 row selected.

SQL> /   COUNT(*)

---

         7

1 row selected.

SQL> /   COUNT(*)

---

         3

1 row selected.

SQL> /   COUNT(*)

---

         6

1 row selected.

SQL> /   COUNT(*)

---

         8

1 row selected.

SQL> /   COUNT(*)

---

         3

1 row selected.

SQL> /   COUNT(*)

---

         0

1 row selected.

SQL> This is 11.1.0.7, 64-bit on Linux, if it matters.

But, I think Vladimir hit the nail on the head. There is no guarantee of read consistency from V$ (or X$ for that matter). So, even if it doesn't make logical sense to have a session that's both STATUS='ACTIVE' and EVENT='SQL*Net message from client', I don't think it's a stretch to see such situations pop up from time to time. It' just a race condition.

Hope that helps,

-Mark

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Vladimir Andreev Sent: Wednesday, June 17, 2009 6:26 PM
To: fmhabash_at_gmail.com; Oracle-L Group Subject: Re: How to make a session active with wait event of 'sql*net message FROM client'?

Hi,
as far as I know, the v$ views are not guaranteed to be consistent, and wait events change quickly. So my theory is that you've seen (in the real-life situation) the status ACTIVE, but before your query got to the wait event it changed.
So if that's true, you may be able to reproduce it by issuing lots ov very short calls to (along the lines of "select 1 from dual" - each one of these gives you 3 or 4 rapid-fire calls - parse, execute, and one or two fetches, depending on array size) and running your query against V$session (10g and above) repeatedly. Of course, if I'm right, reproducing the situation will give you no useful insight - but you may have your reasons... Cheers!
Flado

On 17/06/2009, Fmhabash <fmhabash_at_gmail.com> wrote:
> Hi all, am trying to duplicate a real-life situation where a db had several
> sessions with status of active and wait event of sq*net message FROM client.
> So far, am not able to do that. I tried a session with uncommitted DML or
> waiting on a substitution variable, but both show as inactive.
>
> How can this status/event combination be reproduced?
>
>
> ---------------
> Thank You.
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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Received on Wed Jun 17 2009 - 18:13:37 CDT